Musical Instrument Digital Interface
Overview
 
MIDI is an industry-standard protocol
Communications protocol
A communications protocol is a system of digital message formats and rules for exchanging those messages in or between computing systems and in telecommunications...

, first defined in 1982 by Gordon Hall, that enables electronic musical instrument
Electronic musical instrument
An electronic musical instrument is a musical instrument that produces its sounds using electronics. Such an instrument sounds by outputting an electrical audio signal that ultimately drives a loudspeaker....

s (synthesizer
Synthesizer
A synthesizer is an electronic instrument capable of producing sounds by generating electrical signals of different frequencies. These electrical signals are played through a loudspeaker or set of headphones...

s, drum machine
Drum machine
A drum machine is an electronic musical instrument designed to imitate the sound of drums or other percussion instruments. They are used in a variety of musical genres, not just purely electronic music...

s), computers and other electronic equipment (MIDI controller
MIDI controller
MIDI controller is used in two senses.*In one sense, a controller is hardware or software which generates and transmits MIDI data to MIDI-enabled devices....

s, sound card
Sound card
A sound card is an internal computer expansion card that facilitates the input and output of audio signals to and from a computer under control of computer programs. The term sound card is also applied to external audio interfaces that use software to generate sound, as opposed to using hardware...

s, samplers
Sampler (musical instrument)
A sampler is an electronic musical instrument similar in some respects to a synthesizer but, instead of generating sounds, it uses recordings of sounds that are loaded or recorded into it by the user and then played back by means of a keyboard, sequencer or other triggering device to perform or...

) to communicate and synchronize with each other. MIDI's primary functions include communicating event message
Message passing
Message passing in computer science is a form of communication used in parallel computing, object-oriented programming, and interprocess communication. In this model, processes or objects can send and receive messages to other processes...

s about musical notation
Musical notation
Music notation or musical notation is any system that represents aurally perceived music, through the use of written symbols.-History:...

, pitch
Pitch (music)
Pitch is an auditory perceptual property that allows the ordering of sounds on a frequency-related scale.Pitches are compared as "higher" and "lower" in the sense associated with musical melodies,...

, velocity, control signals for parameters (such as volume, vibrato
Vibrato
Vibrato is a musical effect consisting of a regular, pulsating change of pitch. It is used to add expression to vocal and instrumental music. Vibrato is typically characterised in terms of two factors: the amount of pitch variation and the speed with which the pitch is varied .-Vibrato and...

, panning
Panning (audio)
Panning is the spread of a sound signal into a new stereo or multi-channel sound field. A typical physical recording console pan control is a knob with a pointer which can be placed from the 8 o'clock dial position fully left to the 4 o'clock position fully right...

, cues, and clock signals (to set the tempo
Tempo
In musical terminology, tempo is the speed or pace of a given piece. Tempo is a crucial element of any musical composition, as it can affect the mood and difficulty of a piece.-Measuring tempo:...

)) between two devices in order to complete a signal chain and produce audible sound from a sound source.
Encyclopedia
MIDI is an industry-standard protocol
Communications protocol
A communications protocol is a system of digital message formats and rules for exchanging those messages in or between computing systems and in telecommunications...

, first defined in 1982 by Gordon Hall, that enables electronic musical instrument
Electronic musical instrument
An electronic musical instrument is a musical instrument that produces its sounds using electronics. Such an instrument sounds by outputting an electrical audio signal that ultimately drives a loudspeaker....

s (synthesizer
Synthesizer
A synthesizer is an electronic instrument capable of producing sounds by generating electrical signals of different frequencies. These electrical signals are played through a loudspeaker or set of headphones...

s, drum machine
Drum machine
A drum machine is an electronic musical instrument designed to imitate the sound of drums or other percussion instruments. They are used in a variety of musical genres, not just purely electronic music...

s), computers and other electronic equipment (MIDI controller
MIDI controller
MIDI controller is used in two senses.*In one sense, a controller is hardware or software which generates and transmits MIDI data to MIDI-enabled devices....

s, sound card
Sound card
A sound card is an internal computer expansion card that facilitates the input and output of audio signals to and from a computer under control of computer programs. The term sound card is also applied to external audio interfaces that use software to generate sound, as opposed to using hardware...

s, samplers
Sampler (musical instrument)
A sampler is an electronic musical instrument similar in some respects to a synthesizer but, instead of generating sounds, it uses recordings of sounds that are loaded or recorded into it by the user and then played back by means of a keyboard, sequencer or other triggering device to perform or...

) to communicate and synchronize with each other. MIDI's primary functions include communicating event message
Message passing
Message passing in computer science is a form of communication used in parallel computing, object-oriented programming, and interprocess communication. In this model, processes or objects can send and receive messages to other processes...

s about musical notation
Musical notation
Music notation or musical notation is any system that represents aurally perceived music, through the use of written symbols.-History:...

, pitch
Pitch (music)
Pitch is an auditory perceptual property that allows the ordering of sounds on a frequency-related scale.Pitches are compared as "higher" and "lower" in the sense associated with musical melodies,...

, velocity, control signals for parameters (such as volume, vibrato
Vibrato
Vibrato is a musical effect consisting of a regular, pulsating change of pitch. It is used to add expression to vocal and instrumental music. Vibrato is typically characterised in terms of two factors: the amount of pitch variation and the speed with which the pitch is varied .-Vibrato and...

, panning
Panning (audio)
Panning is the spread of a sound signal into a new stereo or multi-channel sound field. A typical physical recording console pan control is a knob with a pointer which can be placed from the 8 o'clock dial position fully left to the 4 o'clock position fully right...

, cues, and clock signals (to set the tempo
Tempo
In musical terminology, tempo is the speed or pace of a given piece. Tempo is a crucial element of any musical composition, as it can affect the mood and difficulty of a piece.-Measuring tempo:...

)) between two devices in order to complete a signal chain and produce audible sound from a sound source. As an electronic protocol, it is notable for its widespread adoption throughout the music industry.

All MIDI-compatible controllers, musical instruments and MIDI-compatible software
Music sequencer
The music sequencer is a device or computer software to record, edit, play back the music, by handling note and performance information in several forms, typically :...

 follow the same MIDI 1.0
MIDI 1.0
There are two sides to MIDI 1.0: the hardware transport specification describing the electrical and mechanical connection, and the message format specification.- Hardware transport :...

 specification, and thus interpret any given MIDI message the same way, allowing two devices (a trigger device and a sound source) to communicate with and understand each other. MIDI's composition takes advantage of MIDI 1.0
MIDI 1.0
There are two sides to MIDI 1.0: the hardware transport specification describing the electrical and mechanical connection, and the message format specification.- Hardware transport :...

 and General MIDI (GM)
General MIDI
General MIDI or GM is a standardized specification for music synthesizers that respond to MIDI messages. GM was developed by the MIDI Manufacturers Association and the Japan MIDI Standards Committee and first published in 1991...

 technology to allow MIDI data files to be shared between multiple devices, eliminating compatibility issues by using a standard set of commands and parameters. Since MIDI data is stored as the various trigger instructions for any given sound source, the file sizes are considerably smaller than the corresponding audio files

History

By the end of the 1970s, electronic musical devices were becoming increasingly common and affordable. However, devices from different manufacturers were generally not compatible with each other and could not be interconnected. Different interfacing models included analog control voltages at various standards (such as 1 volt
Volt
The volt is the SI derived unit for electric potential, electric potential difference, and electromotive force. The volt is named in honor of the Italian physicist Alessandro Volta , who invented the voltaic pile, possibly the first chemical battery.- Definition :A single volt is defined as the...

 per octave
Octave
In music, an octave is the interval between one musical pitch and another with half or double its frequency. The octave relationship is a natural phenomenon that has been referred to as the "basic miracle of music", the use of which is "common in most musical systems"...

, or the logarithmic "hertz
Hertz
The hertz is the SI unit of frequency defined as the number of cycles per second of a periodic phenomenon. One of its most common uses is the description of the sine wave, particularly those used in radio and audio applications....

 per volt"); analog clock, trigger and "gate" signals (both positive "V-trig" and negative "S-trig" varieties, between −15 V to +15 V); and proprietary digital interfaces such as Roland Corporation
Roland Corporation
is a Japanese manufacturer of electronic musical instruments, electronic equipment and software. It was founded by Ikutaro Kakehashi in Osaka on April 18, 1972, with ¥33 million in capital. In 2005 Roland's headquarters relocated to Hamamatsu in Shizuoka Prefecture. Today it has factories in Japan,...

's DCB
Digital Control Bus
DCB was a proprietary data interchange interface by Roland Corporation, developed in 1981 and introduced in 1982 in their Roland Juno-60 and Roland Jupiter-8 products...

 (digital control bus), the Oberheim
Oberheim
Oberheim Electronics is an American company, founded in 1969 by Tom Oberheim , which manufactured audio synthesizers and a variety of other electronic musical instruments.-Oberheim Electronics:...

 system, and Yamaha
Yamaha
Yamaha may refer to:* Yamaha Corporation, a Japanese company with a wide range of products and services** Yamaha Motor Company, a Japanese motorized vehicle-producing company...

's "keycode" system.

In the late seventies, Dave Smith
Dave Smith (engineer)
Dave Smith is an engineer and guitarist who pioneered many groundbreaking technologies in music technology. Smith was responsible for the first polyphonic and microprocessor-controlled synthesizer, the Prophet 5...

 was working on a polyphonic analog synthesizer which was to become the Prophet 5. Early analog synthesizers could only play one note or "voice" at a time. The keyboard had a single voltage output, and controlled the sound directly, as did each knob, switch and other control on the instrument.

Dave's innovative idea was to create an instrument with multiple identical sound-producing engines ("voices") and make all the parameters of the voices digitally controllable. Now, when the player turned a knob on the front panel, instead of the knob being part of and directly controlling some element of the signal path, its setting would be digitized, and the same parameter could be simultaneously affected on all of the voices. And, instead of having the keyboard control a single note, a microprocessor was used that would rapidly and continuously scan all of the keys to detect which ones were currently pressed, and convert that information to a pitch control that would be assigned to the next available voice. In this manner, the musician playing the instrument would experience it as if the keyboard and all of the knobs and other controls were directly controlling a multi-voice instrument.

This innovation meant two very important things: since all of the controls were digitized, their settings could be remembered, and the synthesizer could be provided a memory wherein "patches" could be stored and instantly recalled. More significantly, it abstracted the keyboard, knobs, pedals, and other controls away from the sound-producing circuitry and made it necessary to develop a protocol for communication between the former and the latter.

Dave Smith had the insight that the data connection could be made accessible with input and output jacks on the instrument, and, if the protocol were standardized between manufacturers, would provide a means for a myriad of instruments and other devices to interoperate, controlling and being controlled by each other at the digital level. Thus, MIDI was born.

Following several months of discussion between US and Japanese manufacturers, in November 1981, audio engineer and synthesizer designer Dave Smith
Dave Smith (engineer)
Dave Smith is an engineer and guitarist who pioneered many groundbreaking technologies in music technology. Smith was responsible for the first polyphonic and microprocessor-controlled synthesizer, the Prophet 5...

 of Sequential Circuits, Inc.
Sequential Circuits
Sequential Circuits Inc. was a California-based synthesizer company that was founded in the early 1970s by Dave Smith and sold to Yamaha Corporation in 1987. The company, throughout its lifespan, pioneered many groundbreaking technologies and design principles that are often taken for granted in...

 proposed a digital standard for musical instruments at the Audio Engineering Society
Audio Engineering Society
Established in 1948, the Audio Engineering Society draws its membership from amongst engineers, scientists, other individuals with an interest or involvement in the professional audio industry. The membership largely comprises engineers developing devices or products for audio, and persons working...

 show in New York. By the time of the January, 1983 Winter NAMM Show
NAMM Show
The NAMM Show is one of the largest music product trade shows in the world, founded in 1901. It is held every January in Anaheim, California, USA, at the Anaheim Convention Center...

, Smith was able to demonstrate a MIDI connection between his Prophet 600 (a later version of the groundbreaking Prophet 5 analog synthesizer) and a Roland JP-6
Roland Jupiter-6
The Roland Jupiter-6 is a synthesizer manufactured by the Roland Corporation introduced in 1983 as a less expensive alternative to the Roland Jupiter-8. The Jupiter-6 is widely considered a workhorse among polyphonic analog synthesizers, capable of producing a wide variety of sounds, such as...

. The MIDI Specification 1.0 was published in August 1983. (See MMA)

MIDI brought an unprecedented state of compatibility which revolutionized the market by ridding musicians of the need for excessive hardware. In the early 1980s, MIDI was a major factor in bringing an end to the "wall of synthesizers" phenomenon in progressive rock band concerts, when keyboard
Keyboard instrument
A keyboard instrument is a musical instrument which is played using a musical keyboard. The most common of these is the piano. Other widely used keyboard instruments include organs of various types as well as other mechanical, electromechanical and electronic instruments...

 performers were often hidden behind huge banks of analog synthesizers and electric pianos. Following the advent of MIDI, many synthesizers were released in rack-mount
19-inch rack
A 19-inch rack is a standardized frame or enclosure for mounting multiple equipment modules. Each module has a front panel that is wide, including edges or ears that protrude on each side which allow the module to be fastened to the rack frame with screws.-Overview and history:Equipment designed...

 versions, which meant that keyboardists could control many different instruments (e.g., synthesizers) from a single keyboard
Musical keyboard
A musical keyboard is the set of adjacent depressible levers or keys on a musical instrument, particularly the piano. Keyboards typically contain keys for playing the twelve notes of the Western musical scale, with a combination of larger, longer keys and smaller, shorter keys that repeats at the...

.

In the 1980s, MIDI facilitated the development of hardware and computer-based sequencers
Music sequencer
The music sequencer is a device or computer software to record, edit, play back the music, by handling note and performance information in several forms, typically :...

, which can be used to record, edit and play back performances. In the years immediately after the 1983 ratification of the MIDI specification, MIDI features were adapted to several early computer platforms including Apple II Plus
Apple II Plus
The Apple II Plus was the second model of the Apple II series of personal computers produced by Apple Computer, Inc. It was sold new from June 1979 to December 1982.-Features:...

 and IIe
Apple IIe
The Apple IIe is the third model in the Apple II series of personal computers produced by Apple Computer. The e in the name stands for enhanced, referring to the fact that several popular features were now built-in that were only available as upgrades and add-ons in earlier models...

, Apple Macintosh, Commodore 64
Commodore 64
The Commodore 64 is an 8-bit home computer introduced by Commodore International in January 1982.Volume production started in the spring of 1982, with machines being released on to the market in August at a price of US$595...

, Commodore Amiga and PC-DOS
PC-DOS
IBM PC DOS is a DOS system for the IBM Personal Computer and compatibles, manufactured and sold by IBM from the 1980s to the 2000s....

. This allowed the development of a market for powerful, inexpensive, and now-widespread computer-based MIDI sequencers. The standard Atari ST
Atari ST
The Atari ST is a home/personal computer that was released by Atari Corporation in 1985 and commercially available from that summer into the early 1990s. The "ST" officially stands for "Sixteen/Thirty-two", which referred to the Motorola 68000's 16-bit external bus and 32-bit internals...

 came equipped with MIDI ports and was commonly used in recording studios for this reason. Synchronization of MIDI sequences is made possible by the use of MIDI timecode
MIDI timecode
MIDI time code , or MIDI time division, embeds the same timing information as standard SMPTE timecode as a series of small 'quarter-frame' MIDI messages. There is no provision for the user bits in the standard MIDI time code messages, and SysEx messages are used to carry this information instead...

, an implementation of the SMPTE time code
SMPTE time code
SMPTE timecode is a set of cooperating standards to label individual frames of video or film with a time code defined by the Society of Motion Picture and Television Engineers in the SMPTE 12M specification...

 standard using MIDI messages, and MIDI timecode has become the standard for digital
Digital
A digital system is a data technology that uses discrete values. By contrast, non-digital systems use a continuous range of values to represent information...

 music synchronization.

In 1991, the MIDI Show Control
MIDI Show Control
MIDI Show Control, or MSC, is a significant Real Time System Exclusive extension of the international Musical Instrument Digital Interface standard...

 (MSC) protocol (in the Real Time System Exclusive subset) was ratified by the MIDI Manufacturers Association
MIDI Manufacturers Association
The MIDI Manufacturers Association is an organization where companies work together to create the standards that assure compatibility among MIDI products. The MMA is a U.S. organization established in 1985 by the original developers of the MIDI 1.0 Specification in 1983. Since 1985 the MMA has...

. The MSC protocol is an industry standard which allows all types of media control devices to talk with each other and with computers to perform show control
Show control
Show control is the use of automation technology to link together and operate multiple entertainment control systems in a coordinated manner. It is distinguished from entertainment control , which coordinates elements within a single entertainment discipline such as lighting, sound, video, rigging...

 functions in live and canned entertainment
Entertainment
Entertainment consists of any activity which provides a diversion or permits people to amuse themselves in their leisure time. Entertainment is generally passive, such as watching opera or a movie. Active forms of amusement, such as sports, are more often considered to be recreation...

 applications. Just like musical MIDI, MSC does not transmit the actual show media: it simply transmits digital data providing information such as the type, timing and numbering of technical cues called during a multimedia
Multimedia
Multimedia is media and content that uses a combination of different content forms. The term can be used as a noun or as an adjective describing a medium as having multiple content forms. The term is used in contrast to media which use only rudimentary computer display such as text-only, or...

 or live theatre
Theatre
Theatre is a collaborative form of fine art that uses live performers to present the experience of a real or imagined event before a live audience in a specific place. The performers may communicate this experience to the audience through combinations of gesture, speech, song, music or dance...

 performance.

Small file sizes made MIDI files a popular way of sharing music on the Internet
Internet
The Internet is a global system of interconnected computer networks that use the standard Internet protocol suite to serve billions of users worldwide...

 in the early to mid 1990s, before broadband
Broadband
The term broadband refers to a telecommunications signal or device of greater bandwidth, in some sense, than another standard or usual signal or device . Different criteria for "broad" have been applied in different contexts and at different times...

 connections made it practical to share files in the MP3
MP3
MPEG-1 or MPEG-2 Audio Layer III, more commonly referred to as MP3, is a patented digital audio encoding format using a form of lossy data compression...

 format. Many gopher, and later web, sites hosted directories of MIDI files created by fans, thus avoiding the copyright issues that would later plague other forms of online music sharing
File sharing
File sharing is the practice of distributing or providing access to digitally stored information, such as computer programs, multimedia , documents, or electronic books. It may be implemented through a variety of ways...

.

MIDI initially made no provision for specifying timbre. In other words, each MIDI synthesizer had its own methods for producing the sound from MIDI instructions, with no standard sounds at all. For example, a producer might want a MIDI file played back through the Microsoft MIDI
General MIDI
General MIDI or GM is a standardized specification for music synthesizers that respond to MIDI messages. GM was developed by the MIDI Manufacturers Association and the Japan MIDI Standards Committee and first published in 1991...

 Synthesizer (included in any Windows operating system) to sound the same or similar on all machines. But because the quality of synthesis hardware might vary widely between machines—one might use a generic sound card, another might use professional-quality synthesis—there was no way to assure that what the listener heard was anything like what the producer intended.

This situation was the impetus for the introduction of General MIDI
General MIDI
General MIDI or GM is a standardized specification for music synthesizers that respond to MIDI messages. GM was developed by the MIDI Manufacturers Association and the Japan MIDI Standards Committee and first published in 1991...

 in 1991. It created a standard set of 128 familiar sound types (piano, organ, guitar, strings). While manufacturers were still unable to decide what 'piano' sounded like, they at least had a standard to aim for and a location in which to place it.

In the early decades of MIDI, computer hardware was not able to play many samples or synthesize quality sounds. Quality hardware was too expensive; sound cards kept the price down, but many relied on unsophisticated synthesis methods to produce audio. As a result the "MIDI sound" acquired a poor reputation with some critics.

MIDI technology was standardized and is maintained by the MIDI Manufacturers Association
MIDI Manufacturers Association
The MIDI Manufacturers Association is an organization where companies work together to create the standards that assure compatibility among MIDI products. The MMA is a U.S. organization established in 1985 by the original developers of the MIDI 1.0 Specification in 1983. Since 1985 the MMA has...

 (MMA). All official MIDI standards are jointly developed and published by the MMA in Los Angeles, California
Los Angeles, California
Los Angeles , with a population at the 2010 United States Census of 3,792,621, is the most populous city in California, USA and the second most populous in the United States, after New York City. It has an area of , and is located in Southern California...

, USA, and for Japan, the MIDI Committee of the Association of Musical Electronics Industry
Association of Musical Electronics Industry
The Association of Musical Electronics Industry is an organization where companies work together to create the standards that assure compatibility among electronic musical instruments, particularly MIDI products. The AMEI is a Japanese organization established in 1996.- External links :*...

 (AMEI) in Tokyo.

Primary reference for MIDI is The Complete MIDI 1.0 Detailed Specification, document version 96.1, available only from MMA in English, or from AMEI in Japanese. Though the MMA site formerly offered free downloads of all MIDI specifications, links to the basic and general detailed specs have been removed. Printed documents can be purchased. However, considerable ancillary material is available at no cost on the website.

Interfaces

The original physical MIDI connection uses DIN 5/180° connectors
DIN connector
A DIN connector is a connector that was originally standardized by the , the German national standards organization. There are DIN standards for a large number of different connectors, therefore the term "DIN connector" alone does not unambiguously identify any particular type of connector unless...

. Opto-isolating
Opto-isolator
In electronics, an opto-isolator, also called an optocoupler, photocoupler, or optical isolator, is "an electronic device designed to transfer electrical signals by utilizing light waves to provide coupling with electrical isolation between its input and output"...

 connections are used, to prevent ground loops
Ground loop (electricity)
In an electrical system, a ground loop usually refers to a current, almost always unwanted, in a conductor connecting two points that are supposed to be at the same potential, often ground, but are actually at different potentials. Ground loops created by improperly designed or improperly installed...

 occurring among connected MIDI devices.

The MIDI transceivers physically and logically separate the input and output lines, meaning that MIDI messages received by a device in the network not intended for that device must be re-transmitted on the output line (MIDI-OUT) by means of a "soft through". This can introduce a delay, one that is long enough to become musically significant on larger MIDI chains.

MIDI-THRU ports started to be added to MIDI-compatible equipment soon after the introduction of MIDI, in order to improve performance. The MIDI-THRU port avoids the aforementioned retransmission delay by linking the MIDI-THRU port to the MIDI-IN socket almost directly.
The difference between the MIDI-OUT and MIDI-THRU ports is that data coming from the MIDI-OUT port has been generated on the device containing that port. Data that comes out of a device's MIDI-THRU port, however, is an exact duplicate of the data received at the MIDI-IN port.

Such chaining together of instruments via MIDI-THRU ports is unnecessary with the use of MIDI "patch bay," "mult" or "Thru" modules consisting of a MIDI-IN connector and multiple MIDI-OUT connectors to which multiple instruments are connected. MIDI Thru Boxes also clean up any skewing of MIDI data bits that might occur at the input stage.

Some equipment has the ability to merge MIDI messages into one stream; this is a specialized function and is not universal to all equipment. Such MIDI Merge boxes digitally merge all MIDI messages appearing at its inputs to its output, which allows a musician to plug in several MIDI controllers (e.g., two musical keyboards and a pedal keyboard) to a single synth voice device such as an EMU
E-mu Systems
E-mu Systems, Inc. is a synthesizer maker and pioneer in samplers and low-cost digital sampling music workstations.-History:Founded in 1971 by Scott Wedge and Dave Rossum, E-mu began making modular synthesizers...

 or Proteus
E-mu Proteus
The E-mu Proteus was a range of digital sound modules and keyboards manufactured in the late twentieth century.-History:E-mu Systems came to prominence in the early 1980s with their relatively affordable Emulator sampler, and subsequently pioneered sample-based synthesis technology with the Proteus...

.

All MIDI compatible instruments have a built-in MIDI. Some computers' sound cards have a built-in MIDI, whereas others require an external MIDI which is connected to the computer via the newer D-subminiature
D-subminiature
The D-subminiature or D-sub is a common type of electrical connector. They are named for their characteristic D-shaped metal shield. When they were introduced, D-subs were among the smaller connectors used on computer systems....

 DA-15 game port
Game port
The game port is a device port found on IBM PC compatible systems throughout the 1980s and 1990s. It was the traditional connector for joystick input devices until superseded by USB in the 21st century....

, a USB connector or by FireWire, Ethernet
Ethernet
Ethernet is a family of computer networking technologies for local area networks commercially introduced in 1980. Standardized in IEEE 802.3, Ethernet has largely replaced competing wired LAN technologies....

 or by MADI (RME standard).
MIDI connectors are defined by the MIDI
MIDI 1.0
There are two sides to MIDI 1.0: the hardware transport specification describing the electrical and mechanical connection, and the message format specification.- Hardware transport :...

 standard. In the 2000s, as computer equipment increasingly used USB connectors, companies began making USB-to-MIDI data interfaces which can transfer MIDI channels to USB-equipped computers. As well, due to the increasing use of computers for music-making and composition, some MIDI keyboard controllers were equipped with USB jacks, so that they can be plugged into computers that are running "software synths" or other music software.

Controllers

In popular parlance, piano-style musical keyboards are called "keyboards", regardless of their functions or type. Amongst MIDI enthusiasts, however, keyboards and other devices used to trigger musical sounds are called "controllers", because with most MIDI set-ups, the keyboard or other device does not make any sounds by itself. MIDI controllers need to be connected to a voice bank or sound module in order to produce musical tones or sounds; the keyboard or other device is "controlling" the voice bank or sound module by acting as a trigger. The most common MIDI controller is the piano-style keyboard, either with weighted or semi-weighted keys, or with unweighted synth-style keys. Keyboard-style MIDI controllers are sold with as few as 25 keys (2 octaves), with larger models such as 49 keys, 61 keys, or even the full 88 keys being available. Different models have different feature sets, the simplest being only keys, while the more extravagant have sliders, knobs, and wheels to provide more controlling options. These include a variety of parameters that can be programmed within the controller, or sent to a computer to control software.

MIDI controllers are also available in a range of other forms, such as electronic drum triggers; pedal keyboards that are played with the feet (e.g., with an organ); wind controllers for performing saxophone-style music; and MIDI guitar synthesizer controllers. A wind controller, is designed for performers who want to play saxophone, clarinet, oboe, bassoon, and other wind instrument sounds with a synthesizer module. When wind instruments are played using a MIDI keyboard, it is hard to reproduce the expressive control found on wind instruments that can be generated with the wind pressure and embouchure. A typical wind controller has an air-pressure level sensor and (usually) a bite sensor in the mouthpiece and touch sensors or keys (commonly approximating saxophone key arrangement) arrayed along the body. Additionally, controls such as buttons, touch sensors and pitch wheels for generating additional midi messages or changing the way the controller behaves (for example, note sustain or octave shifts) are typically located in positions where they can, more or less easily, be accessed while playing. A less common type of wind controller mimics the mechanics of valved brass instruments.

Pad controllers are used by musicians and DJs who make music through use of sampled sounds or short samples of music. Pad controllers often have banks of assignable pads and assignable faders and knobs for transmitting MIDI data or changes; the better-quality models are velocity-sensitive. More rarely, some performers use more specialized MIDI controllers, such as triggers that are affixed to their clothing or stage items (e.g., magicians Penn and Teller's stage show).

A MIDI foot-controller is a pedalboard-style device with rows of switches that control banks of presets, MIDI program change commands and send MIDI note numbers (some also do MIDI merges). Another specialized type of controller is the drawbar controller; it is designed for Hammond organ
Hammond organ
The Hammond organ is an electric organ invented by Laurens Hammond in 1934 and manufactured by the Hammond Organ Company. While the Hammond organ was originally sold to churches as a lower-cost alternative to the wind-driven pipe organ, in the 1960s and 1970s it became a standard keyboard...

 players who have MIDI-equipped organ voice modules. The drawbar controller provides the keyboard player with many of the controls which are found on a vintage 1940s or 1950s Hammond organ, including harmonic drawbars, a rotating speaker
Leslie speaker
The Leslie speaker is a specially constructed amplifier/loudspeaker used to create special audio effects using the Doppler effect. Named after its inventor, Donald Leslie, it is particularly associated with the Hammond organ but is used with a variety of instruments as well as vocals. The...

 speed control switch, vibrato and chorus knobs, and percussion and overdrive controls. As with all controllers, the drawbar controller does not produce any sounds by itself; it only controls a voice module or software sound device.

While most controllers do not produce sounds, there are some exceptions. Some controller keyboards called "performance controllers" have MIDI-assignable keys, sliders, and knobs, which allow the controller to be used with a range of software synthesizers or voice modules; yet at the same time, the controller also has an internal voice module which supplies keyboard instrument sounds (piano, electric piano, clavichord), sampled or synthesized voices (strings, woodwinds), and Digital Signal Processing (distortion, compression, flanging, etc.). These controller keyboards are designed to allow the performer to choose between the internal voices or external modules.

Messages

All MIDI compatible controllers, musical instruments, and MIDI-compatible software
Music sequencer
The music sequencer is a device or computer software to record, edit, play back the music, by handling note and performance information in several forms, typically :...

 follow the same MIDI 1.0
MIDI 1.0
There are two sides to MIDI 1.0: the hardware transport specification describing the electrical and mechanical connection, and the message format specification.- Hardware transport :...

 specification, and thus interpret any given MIDI message the same way, and so can communicate with and understand each other. For example, if a note is played on a MIDI controller, it will sound at the right pitch on any MIDI instrument whose MIDI In connector is connected to the controller's MIDI Out connector.

When a musical performance is played on a MIDI instrument (or controller) it transmits MIDI channel messages from its MIDI Out connector. A typical MIDI channel message sequence corresponding to a key being struck and released on a keyboard is:
  1. The user presses the middle C
    Middle C
    C or Do is the first note of the fixed-Do solfège scale. Its enharmonic is B.-Middle C:Middle C is designated C4 in scientific pitch notation because of the note's position as the fourth C key on a standard 88-key piano keyboard...

     key with a specific velocity
    Keyboard expression
    Keyboard expression often shortened to expression is the ability of a keyboard instrument to respond to the dynamics of the music or change the tone of the sound in response to the way that the performer depresses the keys of the musical keyboard...

     (which is usually translated into the volume of the note but can also be used by the synthesizer to set characteristics of the timbre
    Timbre
    In music, timbre is the quality of a musical note or sound or tone that distinguishes different types of sound production, such as voices and musical instruments, such as string instruments, wind instruments, and percussion instruments. The physical characteristics of sound that determine the...

     as well). The instrument sends one Note-On message.
  2. The user changes the pressure applied on the key while holding it down: a technique called Aftertouch
    Keyboard expression
    Keyboard expression often shortened to expression is the ability of a keyboard instrument to respond to the dynamics of the music or change the tone of the sound in response to the way that the performer depresses the keys of the musical keyboard...

     (can be repeated, optional). The instrument sends one or more Aftertouch messages.
  3. The user releases the middle C key, again with the possibility of velocity of release controlling some parameters. The instrument sends one Note-Off message.


Note-On, Aftertouch, and Note-Off are all channel messages: embedded in the message is one of 16 channel IDs. This enables instruments to be set to respond to messages on specific channels while ignoring all others. (System messages, in contrast, are designed to be responded to by all connected devices.)For the Note-On and Note-Off messages, the MIDI specification defines a number (from 0–127) for every possible note pitch (C, C, D etc.), and this number is included in the message along with the velocity value.

Other performance parameters can be transmitted with channel messages, too. For example, if the user turns the pitch wheel on the instrument, that gesture is transmitted over MIDI using a series of Pitch Bend messages (also a channel message). The musical instrument generates the messages autonomously; all the musician has to do is play the notes (or make some other gesture that produces MIDI messages). This consistent, automated abstraction of the musical gesture could be considered the core of the MIDI standard.

Composition

MIDI composition and arrangement typically takes place using either MIDI sequencing/editing software on PC-type computers, or using specialized hardware music workstation
Music workstation
A music workstation is an electronic musical instrument providing the facilities of:*a sound module,*a music sequencer and* a musical keyboard.It enables a musician to compose electronic music using just one piece of equipment.-History:...

s. Some composers may take advantage of MIDI 1.0
MIDI 1.0
There are two sides to MIDI 1.0: the hardware transport specification describing the electrical and mechanical connection, and the message format specification.- Hardware transport :...

 and General MIDI (GM)
General MIDI
General MIDI or GM is a standardized specification for music synthesizers that respond to MIDI messages. GM was developed by the MIDI Manufacturers Association and the Japan MIDI Standards Committee and first published in 1991...

 technology to allow musical data files to be shared among various electronic instruments by using a standard, portable set of commands and parameters. On the other hand, composers of complex, detailed works to be distributed as produced audio typically use MIDI to control the performance of high-quality digital audio sample
Digital audio sample
Digital audio samples are discrete values which represent the amplitude of an audio signal taken at different points in time.A continuous signal can be sampled at some sampling rate and thus be converted into a digital representation using samples...

s and/or external hardware
Synthesizer
A synthesizer is an electronic instrument capable of producing sounds by generating electrical signals of different frequencies. These electrical signals are played through a loudspeaker or set of headphones...

 or software synthesizer
Software synthesizer
A software synthesizer, also known as a softsynth is a computer program or plug-in for digital audio generation. Computer software which can create sounds or music is not new, but advances in processing speed are allowing softsynths to accomplish the same tasks that previously required dedicated...

s.

Digital Audio Workstations
Digital audio workstation
A digital audio workstation is an electronic system designed solely or primarily for recording, editing and playing back digital audio. DAWs were originally tape-less, microprocessor-based systems such as the Synclavier and Fairlight CMI...

 (DAW) are becoming the one of the most centric and common tools in the studio, and many are specifically designed to work with MIDI as an integral component. Through the use of MIDI mapping, various MIDI controllers can be used to command the program. MIDI piano rolls have been developed in many DAWs so that the recorded MIDI messages can be extensively modified. Virtual Instruments created by third party companies in one of a number of commly used formats (for example, VST
Virtual Studio Technology
Steinberg's Virtual Studio Technology is an interface for integrating software audio synthesizer and effect plugins with audio editors and hard-disk recording systems. VST and similar technologies use digital signal processing to simulate traditional recording studio hardware with software...

 or RTAS
Real Time AudioSuite
Real-Time AudioSuite is a format of audio plug-in developed by Digidesign, currently Avid Technology for their Pro Tools LE, and Pro Tools M-Powered systems, although they can be run on Pro Tools HD and Pro Tools TDM systems. RTAS plug-ins use the processing power of the host computer rather than...

) may be loaded as plug-ins thus providing a virtually limitless supply of sounds for a musician, and are designed to be commanded by MIDI controllers, especially in the DAW environment.

MIDI data files are much smaller than recorded audio waveforms. Many computer-sequencing programs allow manipulation of the musical data such that composing for an entire orchestra
Orchestra
An orchestra is a sizable instrumental ensemble that contains sections of string, brass, woodwind, and percussion instruments. The term orchestra derives from the Greek ορχήστρα, the name for the area in front of an ancient Greek stage reserved for the Greek chorus...

 of sounds is possible. This ability to manipulate musical data has also introduced the concept of surrogate orchestras, providing a combination of half sequenced MIDI recordings and half musicians to make up an entire orchestral arrangement; however, scholars believe surrogate orchestras have the possibility of affecting future live musical performances in which the use of live musicians in orchestral arrangements may cease entirely because the composition of music via MIDI recordings proves to be more efficient and less expensive. Further, the data composed via the sequenced MIDI recordings can then be saved as a Standard MIDI File (SMF), digitally distributed, and reproduced by any computer or electronic instrument that also adheres to the same MIDI, GM, and SMF standards.

Although a music distribution format, the Standard MIDI File was more attractive to computer users before broadband
Broadband Internet access
Broadband Internet access, often shortened to just "broadband", is a high data rate, low-latency connection to the Internet— typically contrasted with dial-up access using a 56 kbit/s modem or satellite Internet with inherently high latency....

 internet became widespread due to its much smaller file size. Also, the advent of high quality audio compression such as the MP3
MP3
MPEG-1 or MPEG-2 Audio Layer III, more commonly referred to as MP3, is a patented digital audio encoding format using a form of lossy data compression...

 format has decreased the relative size advantages of MIDI-encoded music to some degree, though MP3 is still much larger than SMF.

File formats

MIDI messages (along with timing information) can be collected and stored in a computer file
Computer file
A computer file is a block of arbitrary information, or resource for storing information, which is available to a computer program and is usually based on some kind of durable storage. A file is durable in the sense that it remains available for programs to use after the current program has finished...

, in what is commonly called a MIDI file. A number of music file format
File format
A file format is a particular way that information is encoded for storage in a computer file.Since a disk drive, or indeed any computer storage, can store only bits, the computer must have some way of converting information to 0s and 1s and vice-versa. There are different kinds of formats for...

s have been based on the MIDI bytestream. These formats are very compact; a file as small as 10 KiB can produce a full minute of music or more due to the fact that the file stores instructions on how to recreate the sound based on synthesis with a MIDI synthesizer rather than an exact waveform to be reproduced. A MIDI synthesizer could be built into an operating system, sound card, embedded device (e.g. hardware-based synthesizer) or a software-based synthesizer. The file format stores information on what note to play and when, or other important information such as possible pitch bend during the envelope of the note or the note's velocity. Small MIDI file sizes have also been advantageous for applications such as mobile phone ringtones, and some video games.

Standard MIDI (.mid or .smf): The Standard MIDI File (SMF) specification was developed by, and is maintained by, the MIDI Manufacturers Association
MIDI Manufacturers Association
The MIDI Manufacturers Association is an organization where companies work together to create the standards that assure compatibility among MIDI products. The MMA is a U.S. organization established in 1985 by the original developers of the MIDI 1.0 Specification in 1983. Since 1985 the MMA has...

 (MMA). MIDI files are typically created using computer-based sequencing software (or sometimes a hardware-based MIDI instrument or workstation) that organizes MIDI messages into one or more parallel "tracks"
Multitrack recording
Multitrack recording is a method of sound recording that allows for the separate recording of multiple sound sources to create a cohesive whole...

 for independent recording and editing. In most sequencers, each track is assigned to a specific MIDI channel and/or a specific instrument patch; if the attached music synthesizer has a known instrument palette (for example because it conforms to the General MIDI
General MIDI
General MIDI or GM is a standardized specification for music synthesizers that respond to MIDI messages. GM was developed by the MIDI Manufacturers Association and the Japan MIDI Standards Committee and first published in 1991...

 standard), then the instrument for each track may be selected by name. Although most current MIDI sequencer software uses proprietary "session file" formats rather than SMF, almost all sequencers provide export or "Save As..." support for the SMF format. An SMF consists of one header
Header (information technology)
In information technology, header refers to supplemental data placed at the beginning of a block of data being stored or transmitted. In data transmission, the data following the header are sometimes called the payload or body....

 chunk and one or more track chunks. There exist three different SMF formats; the format of a given SMF is specified in its file header. A Format 0 file contains a single track and represents a single song performance. Format 1 may contain any number of tracks, enabling preservation of the sequencer track structure, and also represents a single song performance. Format 2 may have any number of tracks, each representing a separate song performance. Sequencers do not commonly support Format 2. Large collections of SMFs can be found on the web, most commonly with the extension
Filename extension
A filename extension is a suffix to the name of a computer file applied to indicate the encoding of its contents or usage....

 .mid but occasionally with the .smf. These files are most frequently authored with the (rather dubious) assumption that they will only ever be played on General MIDI
General MIDI
General MIDI or GM is a standardized specification for music synthesizers that respond to MIDI messages. GM was developed by the MIDI Manufacturers Association and the Japan MIDI Standards Committee and first published in 1991...

 players.
MIDI Karaoke (.kar): MIDI-Karaoke (which uses the ".kar" file extension) files are an "unofficial" extension of MIDI files, used to add synchronized lyrics to standard MIDI files. SMF players play the music as they would a .mid file but do not display these lyrics unless they have specific support for .kar messages. These often display the lyrics synchronized with the music in "follow-the-bouncing-ball"
Bouncing ball
The bouncing ball is a device used in video recordings to visually indicate the rhythm of a song, helping audiences to sing along with live or prerecorded music...

 or progressive highlighting of the lyric text fashion, essentially turning any PC into a karaoke
Karaoke
is a form of interactive entertainment or video game in which amateur singers sing along with recorded music using a microphone and public address system. The music is typically a well-known pop song minus the lead vocal. Lyrics are usually displayed on a video screen, along with a moving symbol,...

 machine. None of the MIDI-Karaoke file formats are maintained by any standardization body but they follow General MIDI standards.
XMF: The MMA has also defined (and AMEI has approved) a new family of file formats, XMF (Extensible Music File), some of which package SMF chunks with instrument data in DLS format
DLS format
DLS is a family of standardized file formats for digital musical instrument sound banks . The DLS standards also include detailed specifications for how MIDI protocol-controlled music synthesizers should render the instruments in a DLS file...

 (Downloadable Sounds, also an MMA/AMEI specification), to much the same effect as the MOD
MOD (file format)
MOD is a computer file format used primarily to represent music, and was the first module file format. MOD files use the “.MOD” file extension, except on the Amiga where the original trackers instead use a “mod.” prefix scheme, e.g. “mod.echoing”...

 file format. The XMF container is a binary format (not XML
XML
Extensible Markup Language is a set of rules for encoding documents in machine-readable form. It is defined in the XML 1.0 Specification produced by the W3C, and several other related specifications, all gratis open standards....

-based, although the file extensions are similar).
RIFF-RMID: On Microsoft Windows
Microsoft Windows
Microsoft Windows is a series of operating systems produced by Microsoft.Microsoft introduced an operating environment named Windows on November 20, 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces . Microsoft Windows came to dominate the world's personal...

, the system itself uses proprietary RIFF-based MIDI files with the .rmi extension. Note, Standard MIDI Files are not RIFF-compliant. A RIFF-RMID file, however, is simply a Standard MIDI File wrapped in a RIFF (Resource Interchange File Format) chunk. For compatibility reasons many digital musicians overlook this format. One solution to this incompatibility is to extract the data part of the RIFF-RMID chunk, the result will be a regular Standard MIDI File. RIFF-RMID is not an official MMA
MIDI Manufacturers Association
The MIDI Manufacturers Association is an organization where companies work together to create the standards that assure compatibility among MIDI products. The MMA is a U.S. organization established in 1985 by the original developers of the MIDI 1.0 Specification in 1983. Since 1985 the MMA has...

/AMEI
Association of Musical Electronics Industry
The Association of Musical Electronics Industry is an organization where companies work together to create the standards that assure compatibility among electronic musical instruments, particularly MIDI products. The AMEI is a Japanese organization established in 1996.- External links :*...

 MIDI standard.
Extended RMID: In recommended practice RP-29 (http://www.midi.org/about-midi/rp29spec(rmid).pdf), the MMA defined a method for bundling one Standard MIDI file (SMF) image with one Downloadable Sounds (DLS) image, using the RIFF container technology. However, this method was deprecated when the MMA introduced the Extensible Music Format (XMF)
Extensible Music Format (XMF)
XMF is a tree-based digital container format used to bundle music-oriented content, such as a MIDI file and optionally the sounds it uses, liner notes or other content grouped by language-codes....

 which, because of its many additional features, is generally preferred for MIDI-related resource-bundling purposes in the future.
Extended MIDI (.xmi): The XMI format is a proprietary extension of the SMF format introduced by the Miles Sound System
Miles Sound System
Miles Sound System , formerly known as Audio Interface Library , is a sound software system primarily for video games and used mostly as an alternative for low-end audio chipsets. It uses little CPU time while providing adequate audio output. It was originally a middleware driver library for...

, a middleware
Middleware
Middleware is computer software that connects software components or people and their applications. The software consists of a set of services that allows multiple processes running on one or more machines to interact...

 driver
Device driver
In computing, a device driver or software driver is a computer program allowing higher-level computer programs to interact with a hardware device....

 library targeted at PC games
Personal computer game
A PC game, also known as a computer game, is a video game played on a personal computer, rather than on a video game console or arcade machine...

. XMI is not an official MMA/AMEI MIDI standard.

Extensions

Many extensions of the original official MIDI 1.0
MIDI 1.0
There are two sides to MIDI 1.0: the hardware transport specification describing the electrical and mechanical connection, and the message format specification.- Hardware transport :...

 spec have been standardized by MMA/JMSC.

The General MIDI
General MIDI
General MIDI or GM is a standardized specification for music synthesizers that respond to MIDI messages. GM was developed by the MIDI Manufacturers Association and the Japan MIDI Standards Committee and first published in 1991...

 Level 1 ("GM") specification defines the feature set important for MIDI content interoperability across multiple players. It addresses the indeterminacy of the basic MIDI 1.0
MIDI 1.0
There are two sides to MIDI 1.0: the hardware transport specification describing the electrical and mechanical connection, and the message format specification.- Hardware transport :...

 protocol standard regarding the meaning and behaviour of Program Change and Control Change messages. Without GM, different synthesizers can, and actually do, sound completely different in response to the same MIDI messages. General MIDI 1 was introduced in 1991.

In order to improve upon the General MIDI standard, and to take advantage of the advancements in newer synthesizers, both Roland and Yamaha introduced new, proprietary, extended MIDI specifications—dubbed "GS
Roland GS
Roland GS, or just GS, sometimes expanded as General Standard or General Sound, is an extension of General MIDI specification. It requires that all GS-compatible equipment must meet a certain set of features and it documents interpretations of some MIDI commands and bytes sequences, thus defining...

" and "XG", respectively—along with numerous products based correspondingly upon them, designed with stricter requirements, new features, and backward compatibility with the GM specification. GS and XG are not mutually compatible, nor are they official MMA/AMEI MIDI standards. Adoption of each has been limited in general to its respective manufacturer; however, most popular MIDI/music software offerings now include them as built-in selectable options.

Later, after the success of General MIDI was firmly established, member companies of Japan's AMEI
Association of Musical Electronics Industry
The Association of Musical Electronics Industry is an organization where companies work together to create the standards that assure compatibility among electronic musical instruments, particularly MIDI products. The AMEI is a Japanese organization established in 1996.- External links :*...

 developed the General MIDI Level 2 (GM2) specification. Later still, GM2 became the basis of the instrument selection mechanism in Scalable Polyphony MIDI (SP-MIDI), a MIDI variant for mobile applications where different players may have different numbers of musical voices. SP-MIDI is a component of the 3GPP
3GPP
The 3rd Generation Partnership Project is a collaboration between groups of telecommunications associations, known as the Organizational Partners...

 mobile phone terminal multimedia architecture, starting from release 5.

By convention, most MIDI synthesizers generally default to the conventional Western 12-pitch-per-octave, equal temperament
Equal temperament
An equal temperament is a musical temperament, or a system of tuning, in which every pair of adjacent notes has an identical frequency ratio. As pitch is perceived roughly as the logarithm of frequency, this means that the perceived "distance" from every note to its nearest neighbor is the same for...

 tuning system. This tuning system makes many types of music inaccessible, because they depend on different intonation systems. To address this issue in a standardized manner, in 1992 the MMA ratified the MIDI Tuning Standard
MIDI Tuning Standard
MIDI Tuning Standard is a specification of precise musical pitch agreed to by the MIDI Manufacturers Association in the MIDI protocol. MTS allows for both a bulk tuning dump message, giving a tuning for each of 128 notes, and a tuning message for individual notes as they are played.-Frequency...

, or MTS. Instruments that support the MTS standard can be tuned to any desired tuning system by sending the MTS System Exclusive message (a Non-Real Time Sys Ex). The MTS SysEx message uses a three-byte number format to specify a pitch in logarithmic form. This pitch number can be thought of as a three-digit number in base 128. To find the value of the pitch number p that encodes a given frequency f, use the following formula:


For a note in A440 equal temperament, this formula delivers the standard MIDI note number as used in the Note On and Note Off messages. Any other frequencies fill the space evenly.

The MIDI Show Control (MSC) protocol (in the Real Time System Exclusive subset) is an industry standard ratified by the MIDI Manufacturers Association
MIDI Manufacturers Association
The MIDI Manufacturers Association is an organization where companies work together to create the standards that assure compatibility among MIDI products. The MMA is a U.S. organization established in 1985 by the original developers of the MIDI 1.0 Specification in 1983. Since 1985 the MMA has...

 in 1991 which allows all types of media control devices to talk with each other and with computers to perform show control
Show control
Show control is the use of automation technology to link together and operate multiple entertainment control systems in a coordinated manner. It is distinguished from entertainment control , which coordinates elements within a single entertainment discipline such as lighting, sound, video, rigging...

 functions in live and canned entertainment
Entertainment
Entertainment consists of any activity which provides a diversion or permits people to amuse themselves in their leisure time. Entertainment is generally passive, such as watching opera or a movie. Active forms of amusement, such as sports, are more often considered to be recreation...

 applications. Just like musical MIDI (above), MSC does not transmit the actual show media: it simply transmits digital data providing information such as the type, timing and numbering of technical cues called during a multimedia
Multimedia
Multimedia is media and content that uses a combination of different content forms. The term can be used as a noun or as an adjective describing a medium as having multiple content forms. The term is used in contrast to media which use only rudimentary computer display such as text-only, or...

 or live theatre
Theatre
Theatre is a collaborative form of fine art that uses live performers to present the experience of a real or imagined event before a live audience in a specific place. The performers may communicate this experience to the audience through combinations of gesture, speech, song, music or dance...

 performance.

Audio mixers can be controlled with MIDI during console automation
Console automation
Modern digital audio consoles or mixers use automation. Automation allows the console to remember the audio engineer's adjustment of faders during the post-production editing process. A timecode is necessary for synchronization of automation.- Types of Automation :...

.

Alternative hardware transports

In addition to the original 31.25 kbit/s (baud is the signalling rate and is the reciprocal of the shortest signalling element; bits/sec is the data rate) current-loop transported on 5-pin DIN
DIN connector
A DIN connector is a connector that was originally standardized by the , the German national standards organization. There are DIN standards for a large number of different connectors, therefore the term "DIN connector" alone does not unambiguously identify any particular type of connector unless...

, other connectors have been used for the same electrical data, and transmission of MIDI streams in different forms over USB
Universal Serial Bus
USB is an industry standard developed in the mid-1990s that defines the cables, connectors and protocols used in a bus for connection, communication and power supply between computers and electronic devices....

, IEEE 1394 a.k.a FireWire, and Ethernet
Ethernet
Ethernet is a family of computer networking technologies for local area networks commercially introduced in 1980. Standardized in IEEE 802.3, Ethernet has largely replaced competing wired LAN technologies....

 is now common.

USB

A standard for MIDI over USB was developed in 1999 as a joint effort between IBM, Microsoft, Altec Lansing, Roland Corporation, and Philips. To transmit MIDI over USB a Cable Number and Cable Index are added to the message, and the result is encapsulated in a USB packet. The resulting USB message can be double the size of the native MIDI message. Since USB is over 15,000 times faster than MIDI (480,000 kbit/s vs 31.25 kbit/s,) USB has the potential to be much faster. However, due to the nature of USB there is more latency and jitter introduced that is usually in the range of 2 to 10 ms, or about 2 to 10 MIDI commands. Some comparisons done in the early part of the 2000s showed USB to be slightly slower with higher latency, and this is still the case today. Despite the latency and jitter disadvantages, MIDI over USB is increasingly common on musical instruments.

XLR3

Some early MIDI implementations used XLR3 connectors in place of the 5-pin DIN
DIN connector
A DIN connector is a connector that was originally standardized by the , the German national standards organization. There are DIN standards for a large number of different connectors, therefore the term "DIN connector" alone does not unambiguously identify any particular type of connector unless...

. The use of XLR3 connectors allowed the use of standard low-impedance microphone cables as MIDI cables. As the 31.25 kbit/s current-loop requires only three conductors, there was no problem with the loss of two pins. An example of this use is the Octave-Plateau Voyetra-8
Voyetra-8
The Voyetra-8 is an eight voice polyphonic analog synthesizer. Released in 1982 by Octave-Plateau Electronics , it was one of the first analog programmable synthesizers to be rack-mountable and remains one of the most flexible digitally controlled analog...

 synthesizer.

Over a computer network

Compared to USB or FireWire, the computer network
Computer network
A computer network, often simply referred to as a network, is a collection of hardware components and computers interconnected by communication channels that allow sharing of resources and information....

 implementation of MIDI provides network routing capabilities, which are extremely useful in studio or stage environments (USB and FireWire are more restrictive in the connections between computers and devices). Ethernet is moreover capable of providing the high-bandwidth channel that earlier alternatives to MIDI (such as ZIPI
ZIPI
Zeta Instrument Processor Interface was a research project initiated by Zeta Instruments and UC Berkeley's CNMAT...

) were intended to bring.

After the initial fight between different protocols (IEEE-P1639, MIDI-LAN, IETF RTP-MIDI), it appears that IETF's RTP MIDI specification for transport of MIDI streams over computer networks is now spreading faster and faster since more and more manufacturers are integrating RTP-MIDI in their products (Apple, CME, Kiss-Box, etc.). Mac OS X, Windows and Linux drivers are also available to make RTP MIDI devices appear as standard MIDI devices within these operating systems. Additionally, IEEE-P1639 is now a dead project. The other proprietary MIDI/IP protocols are slowly disappearing, since most of them require expensive licensing to be implemented (while RTP MIDI is completely open), or the MIDI implementation does not bring any real advantage (apart from speed) over original MIDI protocol.

The RTP-MIDI protocol has been officially released in public domain by IETF in December 2006 (IETF RFC4695). RTP-MIDI relies on the well-known RTP
Real-time Transport Protocol
The Real-time Transport Protocol defines a standardized packet format for delivering audio and video over IP networks. RTP is used extensively in communication and entertainment systems that involve streaming media, such as telephony, video teleconference applications, television services and...

 (Real Time Protocol) layer (most often running over UDP
User Datagram Protocol
The User Datagram Protocol is one of the core members of the Internet Protocol Suite, the set of network protocols used for the Internet. With UDP, computer applications can send messages, in this case referred to as datagrams, to other hosts on an Internet Protocol network without requiring...

, but compatible with TCP
Transmission Control Protocol
The Transmission Control Protocol is one of the core protocols of the Internet Protocol Suite. TCP is one of the two original components of the suite, complementing the Internet Protocol , and therefore the entire suite is commonly referred to as TCP/IP...

 also), widely used for real-time audio and video streaming over networks. The RTP
Real-time Transport Protocol
The Real-time Transport Protocol defines a standardized packet format for delivering audio and video over IP networks. RTP is used extensively in communication and entertainment systems that involve streaming media, such as telephony, video teleconference applications, television services and...

 layer is easy to implement and requires very little power from the microprocessor, while providing very useful information to the receiver (network latency, dropped packet detection, reordered packets, etc.). RTP-MIDI defines a specific payload type, that allows the receiver to identify MIDI streams.

RTP-MIDI does not alter the MIDI messages in any way (all messages defined in the MIDI norm are transported transparently over the network), but it adds additional features such as timestamping and sysex fragmentation. RTP-MIDI also adds a powerful 'journalling' mechanism that allows the receiver to detect and correct dropped MIDI messages.The first part of RTP-MIDI specification is mandatory for implementors and describes how MIDI messages are encapsulated within the RTP telegram. It also describes how the journalling system works. The journalling system is not mandatory (journalling is not very useful for LAN applications, but it is very important for WAN applications).

The second part of RTP-MIDI specification describes the session control mechanisms that allow multiple stations to synchronize across the network to exchange RTP-MIDI telegrams. This part is informational only, and it is not required.

RTP-MIDI is included in Apple's Mac OS X
Mac OS X
Mac OS X is a series of Unix-based operating systems and graphical user interfaces developed, marketed, and sold by Apple Inc. Since 2002, has been included with all new Macintosh computer systems...

 since 10.4 and iOS since 4.2, as standard MIDI ports (the RTP-MIDI ports appear in Macintosh applications as any other USB or FireWire port. Thus, any MIDI application running on Mac OS X is able to use the RTP-MIDI capabilities in a transparent way). However, Apple's developers considered the session control protocol described in IETF's specification to be too complex, and they created their own session control protocol. Since the session protocol uses a UDP port different from the main RTP-MIDI stream port, the two protocols do not interfere (so the RTP-MIDI implementation in Mac OS X fully complies to the IETF specification).

Apple's implementation has been used as reference by other MIDI manufacturers. A Windows
Microsoft Windows
Microsoft Windows is a series of operating systems produced by Microsoft.Microsoft introduced an operating environment named Windows on November 20, 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces . Microsoft Windows came to dominate the world's personal...

 XP RTP-MIDI driver for their own products only has been released by the Dutch company Kiss-Box, another Windows
Microsoft Windows
Microsoft Windows is a series of operating systems produced by Microsoft.Microsoft introduced an operating environment named Windows on November 20, 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces . Microsoft Windows came to dominate the world's personal...

 RTP-MIDI driver compatible to Windows XP up to Windows 7 (32bit and 64bit) has also been released and a Linux implementation is currently under development by the Grame association. So it seems probable that the Apple's implementation will become the "de-facto" standard (and could even become the MMA reference implementation).

Converting instruments to MIDI

Some older instruments, for example electronic organs built in the 1970s and 1980s, are becoming beyond repair, due to lack of spares and/or of technicians trained on such equipment. The best candidates for upgrade are what are referred to as "Console" sized, or have at least 2x keyboards of 61 notes, and at least a 25 note (preferably 32 note concave) pedal board. Smaller "Spinet" sized organs are probably not considered worthy of conversion.
In some cases, they can be modified into MIDI instruments. Terms coined from MIDI + modification are often used, such as midification or to midify.

An old electronic organ could have almost all of its discrete component electronics replaced by modern circuitry which will cause the instrument to output MIDI signals. The instrument would then become a specialised MIDI keyboard. Its MIDI output would need to be fed to a MIDI engine of some sort.

See for example: Midification of an Organ

New electronic keyboards have MIDI functions as standard and can be connected to the computers with a PC-to-MIDI circuit or simply via USB.
Other forms of MIDI controllers include wind controllers, drums, guitars, accordion and many others.

Old synthesizers are not often modified to transmit MIDI but people sometimes modify them to receive it. The modification involves adding a circuit board that converts digital MIDI signals into analog Control Voltages, as well as adding a MIDI jack. These circuit boards, often called MIDI-to-CV/Gate converters, also allow analog synthesizers to be played while receiving edit filter and envelope parameters from a modern MIDI device. The circuit boards are usually designed specially for one model of synthesizer and it takes some expertise to install them. This allows pre-MIDI analog synthesizers to be controlled by digital sequencers, whereas they formerly required the user to actually play them.

Other applications

MIDI 1.0
MIDI 1.0
There are two sides to MIDI 1.0: the hardware transport specification describing the electrical and mechanical connection, and the message format specification.- Hardware transport :...

 is also used as a control protocol in applications other than music, including:
  • show control
    Show control
    Show control is the use of automation technology to link together and operate multiple entertainment control systems in a coordinated manner. It is distinguished from entertainment control , which coordinates elements within a single entertainment discipline such as lighting, sound, video, rigging...

  • theatre lighting
  • special effects
  • sound design
    Sound design
    Sound design is the process of specifying, acquiring, manipulating or generating audio elements. It is employed in a variety of disciplines including filmmaking, television production, theatre, sound recording and reproduction, live performance, sound art, post-production and video game software...

  • karaoke
    Karaoke
    is a form of interactive entertainment or video game in which amateur singers sing along with recorded music using a microphone and public address system. The music is typically a well-known pop song minus the lead vocal. Lyrics are usually displayed on a video screen, along with a moving symbol,...

  • VJ-ing
    VJ (video performance artist)
    VJing is a broad designation for realtime visual performance. Characteristics of VJing are the creation or manipulation of imagery in realtime through technological mediation and for an audience, in synchronization to music. VJing often takes place at events such as concerts, nightclubs, music...

  • recording system synchronization
  • audio processor control
  • Digital DJing otherwise known as Controllerism
    Controllerism
    Controllerism is the art and practice of using musical software controllers, e.g. MIDI, Open Sound Control , joystick, etc., to build upon, mix, scratch, remix, effect, modify, or otherwise create music, usually by a Digital DJ or "controllerist". Controllerism developed at the peak of USB MIDI...

  • computer networking, as solely demonstrated by the early first-person shooter
    First-person shooter
    First-person shooter is a video game genre that centers the gameplay on gun and projectile weapon-based combat through first-person perspective; i.e., the player experiences the action through the eyes of a protagonist. Generally speaking, the first-person shooter shares common traits with other...

     game MIDI Maze
    MIDI Maze
    MIDI Maze is an early first person shooter maze video game for the Atari ST developed by Xanth Software F/X, published by Hybrid Arts, and released around 1987. It owes a significant debt to what may be the first of its genre, Maze War...

    , 1987
  • animatronic figure control
  • animation parameter control, as demonstrated by Apple Motion
    Apple Motion
    Motion is a software application produced by Apple Inc. for their Mac OS X operating system. It is used to create and edit motion graphics, titling for video production and film production, and 2D and 3D compositing for visual effects.-History:...

     v2
  • lighting control is accomplished through the MIDI Show Control protocol which was standardised in 1991.

Beyond MIDI 1.0

Although traditional MIDI connections work well for most purposes, a number of newer message protocols and hardware transports have been proposed over the years to try to take the idea to the next level. Some of the more notable efforts include:
  • The Open Sound Control (OSC) protocol was developed at CNMAT
    CNMAT
    CNMAT , The Center for New Music and Audio Technologies, is a multidisciplinary research center within University of California, Berkeley Department of Music. The Center's goal is to provide a common ground where music, cognitive science, computer science, and other disciplines meet to...

    . OSC has been implemented in the well-known software synthesizer
    Software synthesizer
    A software synthesizer, also known as a softsynth is a computer program or plug-in for digital audio generation. Computer software which can create sounds or music is not new, but advances in processing speed are allowing softsynths to accomplish the same tasks that previously required dedicated...

     Reaktor
    Reaktor
    Reaktor is a graphical modular software music studio of proprietary license developed by Native Instruments. It lets musicians and sound specialists design and build their own instruments, samplers, effects and sound design tools. It is supplied with many ready-to-use instruments and effects, from...

    , in other innovative projects including SuperCollider
    Supercollider
    A Supercollider is a high energy particle accelerator. The term may refer to:* Superconducting Super Collider, planned 80 km project in Texas, canceled in 1993...

    , Pure Data
    Pure Data
    Pure Data is a visual programming language developed by Miller Puckette in the 1990s for creating interactive computer music and multimedia works. While Puckette is the main author of the program, Pd is an open source project with a large developer base working on new extensions to it. It is...

    , Isadora
    Isadora (software)
    Isadora is a proprietary graphic programming environment for Mac OS X and Microsoft Windows, with emphasis on real-time manipulation of digital video. It has support for Open Sound Control. Isadora was designed by Mark Coniglio.-External links:* * * *...

    , Max/MSP, Csound
    Csound
    Csound is a computer programming language for dealing with sound, also known as a sound compiler or an audio programming language, or more precisely, a C-based audio DSL. It is called Csound because it is written in C, as opposed to some of its predecessors...

    , vvvv
    Vvvv
    vvvv is a general purpose toolkit with a special focus on real time video synthesis and programming large media environments with physical interfaces, real-time motion graphics, audio and video...

    , ChucK
    ChucK
    ChucK is a concurrent, strongly timed audio programming language for real-time synthesis, composition, and performance, which runs on Mac OS X, Linux, Microsoft Windows, and iPhone/iPad. It is designed to favor readability and flexibility for the programmer over other considerations such...

    , Quartz Composer
    Quartz Composer
    Quartz Composer is a node-based visual programming language provided as part of the Xcode development environment in Mac OS X for processing and rendering graphical data....

     and LuaAV as well as in many general purpose programming languages such as C
    C (programming language)
    C is a general-purpose computer programming language developed between 1969 and 1973 by Dennis Ritchie at the Bell Telephone Laboratories for use with the Unix operating system....

     (liblo), Python
    Python (programming language)
    Python is a general-purpose, high-level programming language whose design philosophy emphasizes code readability. Python claims to "[combine] remarkable power with very clear syntax", and its standard library is large and comprehensive...

     (pyliblo), Haskell
    Haskell (programming language)
    Haskell is a standardized, general-purpose purely functional programming language, with non-strict semantics and strong static typing. It is named after logician Haskell Curry. In Haskell, "a function is a first-class citizen" of the programming language. As a functional programming language, the...

     (hosc), Scheme (sosc), Java (programming language)
    Java (programming language)
    Java is a programming language originally developed by James Gosling at Sun Microsystems and released in 1995 as a core component of Sun Microsystems' Java platform. The language derives much of its syntax from C and C++ but has a simpler object model and fewer low-level facilities...

    (JavaOSC, oscP5 for Processing) and Pure
    Pure (programming language)
    Pure is a dynamically typed, functional programming language based on term rewriting. It has facilities for user-defined operator syntax, macros, multiple-precision numbers, and compilation to native code through the LLVM...

     (pure-liblo). The Lemur Input Device
    Lemur Input Device
    The Lemur Input Device was a highly-customizable multi-touch device from French company JazzMutant which serves as a controller for musical devices such as synthesizers and mixing consoles as well as for other media applications such as video performances...

    , a customizable touch panel with MIDI controller-type functions, also uses OSC. OSC differs from MIDI 1.0
    MIDI 1.0
    There are two sides to MIDI 1.0: the hardware transport specification describing the electrical and mechanical connection, and the message format specification.- Hardware transport :...

     over traditional 5-pin DIN in that it can run at broadband speeds when sent over Ethernet
    Ethernet
    Ethernet is a family of computer networking technologies for local area networks commercially introduced in 1980. Standardized in IEEE 802.3, Ethernet has largely replaced competing wired LAN technologies....

     connections. However, the differences are smaller compared to MIDI when run at broadband speeds over Ethernet connections. Few mainstream musical applications and no standalone instruments support the protocol so far, making whole-studio interoperability problematic. OSC is not owned by any private company; neither is it maintained by any standards organization. Since September 2007, there is a proposal for a common namespace within OSC for communication between controllers, synthesizers and hosts. This, too, would not be maintained by any standards organization.
  • Yamaha has its mLAN
    MLAN
    mLAN, short for Music Local Area Network, is a protocol for synchronized transmission and management of multi-channel digital audio, video, control signals and multi-port MIDI over a network. It exploits several features of the IEEE 1394 standard, also known as FireWire, upon which it is based, to...

     protocol, which is based on the IEEE 1394 transport (also known as FireWire) and carries multiple MIDI 1.0
    MIDI 1.0
    There are two sides to MIDI 1.0: the hardware transport specification describing the electrical and mechanical connection, and the message format specification.- Hardware transport :...

     message channels and multiple audio channels. mLAN is not maintained by a standards organization as it is a proprietary protocol. mLAN is open for licensing, although covered by patents owned by Yamaha.
  • Development of a version of MIDI for new products which is fully backward compatible is now under discussion in the MMA. First announced as "HD-MIDI" in 2005 and tentatively called "HD Protocol" since 2008, this new standard would support modern high-speed transports, provide greater range and/or resolution in data values, increase the number of Channels, and support the future introduction of entirely new kinds of messages. Representatives from all sizes and types of companies are involved, from the smallest speciality show control operations to the largest musical equipment manufacturers. No technical details or projected completion dates have been announced as of 2011, however the MMA indicates that a draft of the HD Protocol and an UDP
    User Datagram Protocol
    The User Datagram Protocol is one of the core members of the Internet Protocol Suite, the set of network protocols used for the Internet. With UDP, computer applications can send messages, in this case referred to as datagrams, to other hosts on an Internet Protocol network without requiring...

    -based transport
    Transport layer
    In computer networking, the transport layer or layer 4 provides end-to-end communication services for applications within a layered architecture of network components and protocols...

     is currently being reviewed by its members. Various transports have been proposed for use for the HD-Protocol physical layer, including a call for ACN
    Architecture for Control Networks
    Architecture for Control Networks is a suite of network protocols for theatrical control being developed by Entertainment Services and Technology Association...

     to be used as the sole or primary transport in show control environments.

MIDI software

There is a wide range of MIDI software available such as auto accompaniment applications, notation programs, music teaching software, music producing, games, DJ/remix environments and so on.

virtual MIDI cable driver

Some software company implement virtual midi and audio driver that is sometime compatible with 64 bits

See also

  • Comparison of MIDI standards
    Comparison of MIDI standards
    This table provides summary of comparison of various MIDI enhancement standards by various parameters.- References :* , an extensive guide to various models and their capabilities* , a comparison article...

  • DIN sync
    DIN Sync
    The SYNC standard, often called "DIN sync" or "sync24" , defines an interface for electronic music instruments. It was introduced in the 1980s by Roland Corporation for synchronization of music sequencers, drum machines, arpeggiators and similar devices. The SYNC standard uses the signals clock ...

  • List of MIDI editors and sequencers
  • MIDI beat clock
    MIDI beat clock
    MIDI beat clock is a clock signal that is broadcast via MIDI to ensure that several MIDI-enabled devices such as a synthesizer or music sequencer stay in synchronization. It is not MIDI timecode....

  • Midiboard
    Midiboard
    Midiboard was broadly understood to be a contraction of Midi and Piano keyboard, and, to some extent, the term became synonymous with keyboards sold without sound synthesis during the later part of the 1980s to address the needs of performance artists who needed a master keyboard to control racks...

  • MIDI Machine Control
    MIDI Machine Control
    MIDI Machine Control, or MMC, a subset of the MIDI specification, provides specific commands for controlling recording equipment such as multi-track recorders....

  • MIDI mockup
    Midi mockup
    A MIDI mockup is an extensive demo of a recording project built using samplers to stand in for acoustic instruments.These extensive demos are frequently used in projects requiring large budgets to record, such as film scores...


External links

  • English-language MIDI specs at the MIDI Manufacturers Association
    MIDI Manufacturers Association
    The MIDI Manufacturers Association is an organization where companies work together to create the standards that assure compatibility among MIDI products. The MMA is a U.S. organization established in 1985 by the original developers of the MIDI 1.0 Specification in 1983. Since 1985 the MMA has...

  • Japanese-language MIDI specs at the Association of Musical Electronics Industry
    Association of Musical Electronics Industry
    The Association of Musical Electronics Industry is an organization where companies work together to create the standards that assure compatibility among electronic musical instruments, particularly MIDI products. The AMEI is a Japanese organization established in 1996.- External links :*...

  • Standard MIDI-File Format Spec. 1.1 by “The International MIDI Association”
The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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