Delay (audio effect)
Delay is an audio effect which records an input signal
Audio signal processing
Audio signal processing, sometimes referred to as audio processing, is the intentional alteration of auditory signals, or sound. As audio signals may be electronically represented in either digital or analog format, signal processing may occur in either domain...

 to an audio storage medium, and then plays it back after a period of time. The delayed signal may either be played back multiple times, or played back into the recording again, to create the sound of a repeating, decaying echo
Echo (phenomenon)
In audio signal processing and acoustics, an echo is a reflection of sound, arriving at the listener some time after the direct sound. Typical examples are the echo produced by the bottom of a well, by a building, or by the walls of an enclosed room and an empty room. A true echo is a single...


Early delay systems

The first delay effects were achieved using tape loops improvised on reel-to-reel magnetic recording systems. By shortening or lengthening the loop of tape and adjusting the read and write heads, the nature of the delayed echo could be controlled. This technique was most common among early composers of Musique concrète
Musique concrète
Musique concrète is a form of electroacoustic music that utilises acousmatic sound as a compositional resource. The compositional material is not restricted to the inclusion of sounds derived from musical instruments or voices, nor to elements traditionally thought of as "musical"...

 (Pierre Schaeffer
Pierre Schaeffer
Pierre Henri Marie Schaeffer was a French composer, writer, broadcaster, engineer, musicologist and acoustician of the 20th century. His innovative work in both the sciences —particularly communications and acoustics— and the various arts of music, literature and radio presentation after the end...

), and composers such as Karlheinz Stockhausen
Karlheinz Stockhausen
Karlheinz Stockhausen was a German composer, widely acknowledged by critics as one of the most important but also controversial composers of the 20th and early 21st centuries. Another critic calls him "one of the great visionaries of 20th-century music"...

, who had sometimes devised elaborate systems involving long tapes and multiple recorders and playback systems, collectively processing the input of a live performer or ensemble. Audio engineers working in popular music
Popular music
Popular music belongs to any of a number of musical genres "having wide appeal" and is typically distributed to large audiences through the music industry. It stands in contrast to both art music and traditional music, which are typically disseminated academically or orally to smaller, local...

 quickly adapted similar techniques, to augment their use of plate reverb
Reverberation is the persistence of sound in a particular space after the original sound is removed. A reverberation, or reverb, is created when a sound is produced in an enclosed space causing a large number of echoes to build up and then slowly decay as the sound is absorbed by the walls and air...

 and other studio technologies designed to simulate natural echo.

Analog delay

Before the invention of audio delay technology, music employing a delayed echo had to be recorded in a naturally reverberant space, often an inconvenience for musicians and engineers. The popularity of an easy-to-implement real-time echo effect led to the production of systems offering an all-in-one effects unit
Effects unit
Effects units are electronic devices that alter how a musical instrument or other audio source sounds. Some effects subtly "color" a sound, while others transform it dramatically. Effects are used during live performances or in the studio, typically with electric guitar, keyboard and bass...

 that could be adjusted to produce echoes of any interval or amplitude. The presence of multiple "taps" (playback heads
Tape head
A tape head is a type of transducer used in tape recorders to convert electrical signals to magnetic fluctuations and vice versa.-Principles of operation:...

) made it possible to have delays at varying rhythmic intervals; this allowed musicians an additional means of expression over natural periodic echoes.

Many delay processors based on analog tape recording, such as Ray Butts' Echosonic (1952), Mike Battle's Echoplex
The Echoplex is a tape delay effect, first made in 1959. Designed by Mike Battle, the Echoplex set a standard for the effect in the 1960s and was used by some of the most notable guitar players of the era; original Echoplexes are highly sought after....

 (1959), or the Roland Space Echo (1973), used magnetic tape
Magnetic tape
Magnetic tape is a medium for magnetic recording, made of a thin magnetizable coating on a long, narrow strip of plastic. It was developed in Germany, based on magnetic wire recording. Devices that record and play back audio and video using magnetic tape are tape recorders and video tape recorders...

 as their recording and playback medium. Electric motors guided a tape loop through a device with a variety of mechanisms allowing modification of the effect's parameters. In the case of the popular Echoplex EP-2, the play head was fixed, while a combination record and erase head was mounted on a slide, thus the delay time of the echo was adjusted by changing the distance between the record and play heads. In the Space Echo, all of the heads are fixed, but the speed of the tape could be adjusted, changing the delay time. Thin magnetic tape was not entirely suited for continuous operation, however, so the tape loop had to be replaced from time to time to maintain the audio fidelity
"Fidelity" is the quality of being faithful or loyal. Its original meaning regarded duty to a lord or a king, in a broader sense than the related concept of fealty. Both derive from the Latin word fidēlis, meaning "faithful or loyal"....

 of the processed sounds.

The Binson Echorec, another popular unit, used a rotating magnetic drum as its storage medium. This provided an advantage over tape, as the durable drums were able to last for many years with little deterioration in the audio quality. Other devices used spinning magnetic discs, not entirely unlike those used in modern hard disk drives
Hard disk
A hard disk drive is a non-volatile, random access digital magnetic data storage device. It features rotating rigid platters on a motor-driven spindle within a protective enclosure. Data is magnetically read from and written to the platter by read/write heads that float on a film of air above the...


Robert Fripp
Robert Fripp
Robert Fripp is an English guitarist, composer and record producer. He was ranked 42nd on Rolling Stone magazine's 2003 list of the "100 Greatest Guitarists of All Time" and #47 on’s "Top 50 Guitarists of All Time". Among rock guitarists, Fripp is a master of crosspicking, a technique...

 used two Revox
ReVox is a brand name of Swiss audio equipment created by Studer on March 27, 1951.The ReVox brand name was spun off into Studer Revox AG in 1990. During Studer's acquisition by Harman International Industries, Revox was sold separately to a group of private investors...

 reel to reel tape recorders to achieve very long delay times for solo guitar performance. He dubbed this technology
Frippertronics was a specific tape looping technique used by Robert Fripp. It evolved from a system of tape looping originally developed in the electronic music studios of the early 1960s that was first used by composers Terry Riley and Pauline Oliveros and made popular through its use in ambient...

", and used it in a number of recordings. John Martyn is widely acclaimed as the pioneer of the echoplex. Perhaps the earliest indication of his use can be heard on the songs Would You Believe Me and The Ocean on the album Stormbringer
Stormbringer is the name of the infamous black sword featured in a number of fantasy stories by the author Michael Moorcock. Created by the forces of Chaos, it is described as a huge, black sword covered with strange runes carved deep into its blade...

released in February 1970. This was a first taste of things to come from Martyn’s interest in electronics and the boundless possibilities of electric music. Glistening Glyndebourne on the album Bless The Weather
Bless the Weather
Bless the Weather is a 1971 album by John Martyn and marks his return as a solo artist having released two albums with his wife Beverley Martyn. When it was released it garnered his best reviews to date, and remains a firm favourite among fans, featuring such standards as "Head and Heart" and the...

(1971) showcased his developing technique of playing acoustic guitar through the echoplex to stunning effect. He later went on to experiment with a fuzz box, a volume/wah wah pedal and the echoplex on highly acclaimed Inside Out
Inside Out (John Martyn album)
Inside Out is an album released in 1973 by British singer-songwriter John Martyn. It was his fifth solo album, and his seventh if one includes the albums he made with his wife, Beverley...

(1973) and One World
One World (John Martyn album)
One World is a 1977 album by John Martyn. One of his more experimental works, it features atmospheric, reggae influenced rhythms and free-flowing, jazzy arrangements. Acclaimed for its collaborative spirit, the album includes contributions from Lee Perry on "Big Muff", and Steve Winwood...

(1977). Martyn is cited as an inspiration by many musicians including U2
U2 are an Irish rock band from Dublin. Formed in 1976, the group consists of Bono , The Edge , Adam Clayton , and Larry Mullen, Jr. . U2's early sound was rooted in post-punk but eventually grew to incorporate influences from many genres of popular music...

's The Edge
The Edge
David Howell Evans , more widely known by his stage name The Edge , is a musician best known as the guitarist, backing vocalist, and keyboardist of the Irish rock band U2. A member of the group since its inception, he has recorded 12 studio albums with the band and has released one solo record...


Often incorporating vacuum tube
Vacuum tube
In electronics, a vacuum tube, electron tube , or thermionic valve , reduced to simply "tube" or "valve" in everyday parlance, is a device that relies on the flow of electric current through a vacuum...

-based electronics, surviving analog delay units are sought by modern musicians who wish to employ some of the timbres achievable with this technology.

Solid state delay units using analog bucket brigade delay circuits became available in the 1970s and were briefly a mainstream alternative to tape echo. Though solid state analog delays are less flexible than digital delays and generally have shorter delay times, several classic models such as the discontinued Boss DM-2 are still sought after for their "warmer", more natural echo quality and progressively decaying echos. Additionally, several companies make new analog delays. Old delay systems like the Roland Space Echo and Echoplex
The Echoplex is a tape delay effect, first made in 1959. Designed by Mike Battle, the Echoplex set a standard for the effect in the 1960s and was used by some of the most notable guitar players of the era; original Echoplexes are highly sought after....

 are still highly regarded and used with some frequency by modern bands.

Digital delay

The availability of inexpensive digital signal processing
Digital signal processing
Digital signal processing is concerned with the representation of discrete time signals by a sequence of numbers or symbols and the processing of these signals. Digital signal processing and analog signal processing are subfields of signal processing...

 electronics in the late 1970s and 1980s led to the development of the first 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...

 delay effects. Initially, they were only available in expensive rack mounted units but eventually as costs came down and the electronics grew smaller, they became available in the form of foot pedals. The first digital delay offered in a pedal was the Boss
Boss Corporation
Boss is a manufacturer of effects pedals for electric guitar and bass guitar. It is a division of the Roland Corporation, a Japanese manufacturer that specializes in musical equipment and accessories...

 DD-2 in 1984. Rack mounted delay units evolved into digital reverb units and on to digital multieffects units capable of more sophisticated effects than pure delay, such as reverb and Audio timescale-pitch modification
Audio timescale-pitch modification
Time stretching is the process of changing the speed or duration of an audio signal without affecting its pitch.Pitch scaling or pitch shifting is the opposite: the process of changing the pitch without affecting the speed...


Digital delay systems function by sampling the input signal through an analog-to-digital converter
Analog-to-digital converter
An analog-to-digital converter is a device that converts a continuous quantity to a discrete time digital representation. An ADC may also provide an isolated measurement...

, after which the signal is passed through a series of digital signal processors that record it into a storage buffer
Buffer (computer science)
In computer science, a buffer is a region of a physical memory storage used to temporarily hold data while it is being moved from one place to another. Typically, the data is stored in a buffer as it is retrieved from an input device or just before it is sent to an output device...

, and then play back the stored audio based on parameters set by the user. The delayed ("wet") output may be mixed with the unmodified ("dry") signal after, or before, it is sent to a digital-to-analog converter
Digital-to-analog converter
In electronics, a digital-to-analog converter is a device that converts a digital code to an analog signal . An analog-to-digital converter performs the reverse operation...

 for output.

Many modern digital delays present an extensive array of options, including a control over the time before playback of the delayed signal. Most also allow the user to select the overall level of the processed signal in relation to the unmodified one, or the level at which the delayed signal is fed back into the buffer, to be repeated again. Some systems today allow more exotic controls, such as the ability to add an audio filter
Audio filter
An audio filter is a frequency dependent amplifier circuit, working in the audio frequency range, 0 Hz to beyond 20 kHz. Many types of filters exist for applications including graphic equalizers, synthesizers, sound effects, CD players and virtual reality systems.Being a frequency dependent...

, or to play back the buffer's contents in reverse.

As digital memory became cheaper in the 80s, units like Lexicon
Lexicon (company)
Lexicon is an American audio equipment manufacturing company founded in 1971 and owned by Harman International Industries. Lexicon's roots began in 1969 with the founding of American Data Sciences by MIT professor Dr...

 PCM84, Roland
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,...

 SDE-3000, TC Electronic
TC Electronic
TC Electronic is a Danish audio equipment manufacturer.Its current product ranges include guitar effects, bass amplification, computer audio interfaces, audio plug-in software, live sound equalisers, studio and post production equipment, studio effect processors and broadcast loudness processors...

 2290 offered above 3 seconds delay time, enough to create background loops, rhythms and phrases. The 2290 was upgradable to 32 seconds and Electro-Harmonix
Electro-Harmonix is a New York-based company that makes high-end electronic audio processors. The company was founded by Mike Matthews in 1968. They are most famous for a series of popular guitar effects pedals introduced in the 1970s and 1990s....

 offered a 16-second delay and looping machine.

From delay to loop

While the mentioned long delay units were a bit clumsy to create loops, the Paradis LOOP Delay, created in 1992, was the first unit with dedicated looping functions Record, Overdub, Multiply, Insert, Replace, ... Gibson
Gibson may refer to:* Gibson Amphitheatre* Gibson Appliance* Gibson Girl* Gibson Guitar Corporation* Gibson * Gibson Generating Station-Places:In the United States:* Gibson, Arkansas* Gibson, Georgia* Gibson, Iowa* Gibson, Louisiana...

 manufactured a slightly improved version as Echoplex Digital Pro  until 2006. Its software Aurisis LOOP is also the last loop tool based on a continuous memory structure as used by tape and digital delays. Most following looper
Looper are a Scottish indie-pop band, fronted by Stuart David, former Belle and Sebastian bassist.The band formed in 1998 for a show at the Glasgow School of Art and released their first single "Impossible Things" on the Subpop label a few months later....

s repeat samples and thus have little in common with a digital delay, the exceptions being Maneco's early loopers, the Boss DD-20 in digital delay mode and the Pigtronix Echolution.

Computer software

A natural development from digital delay-processing hardware was the appearance of software-based delay systems. In large part, this coincided with the popularity of both professional and consumer audio editing software. Software delays, in many cases, offer much greater flexibility than even the most recent digital hardware delays. Abundant system memory on modern personal computers offers practically limitless storage for the audio buffer, and the natural efficiency of audio delay algorithms has made the implementation trivial for delays offering shifting or random delay times, or the insertion of other audio effects during the feedback process. Many authors of software plugins have added functionality to emulate the sounds of the earlier analog units.

Software-based delays are most popular today among musicians in electronic genres
Electronic music
Electronic music is music that employs electronic musical instruments and electronic music technology in its production. In general a distinction can be made between sound produced using electromechanical means and that produced using electronic technology. Examples of electromechanical sound...

 or those who prefer to audition the effect in a digital audio editing and mixing environment
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...



In popular and electronic music, electric guitarists use delay to produce densely overlaid textures of notes with rhythms complementary to the music. Vocalists and instrumentalists use it to add a dense or ethereal quality to their singing or playing. Extremely long delays of 10 seconds or more are often used to create loops of a whole musical phrase.

Echoplex is a term often applied to the use of multiple echoes which recur in approximate synchronization with a musical rhythm, so that the notes played combine and recombine in interesting ways. In fact, it was the name of a particular delay unit, the Maestro Echoplex
The Echoplex is a tape delay effect, first made in 1959. Designed by Mike Battle, the Echoplex set a standard for the effect in the 1960s and was used by some of the most notable guitar players of the era; original Echoplexes are highly sought after....


Doubling echo is produced by adding short-range delay to a recorded sound. Delays of thirty to fifty milliseconds are the most common; longer delay times become slapback echo. Mixing the original and delayed sounds creates an effect similar to doubletracking
Double tracking is an audio recording technique in which a performer sings or plays along with their own prerecorded performance, usually to produce a stronger or "bigger" sound than can be obtained with a single voice or instrument. It is a form of overdubbing; the distinction comes from the...

, or unison performance.

Slapback echo uses a longer delay time (seventy-five to 250 milliseconds), with little or no feedback. The effect is characteristic of vocals on 1950s rock-n-roll records, particularly those issued by Sun
Sun Records
Sun Records is a record label founded in Memphis, Tennessee, starting operations on March 27, 1952.Founded by Sam Phillips, Sun Records was known for giving notable musicians such as Elvis Presley , Carl Perkins, Roy Orbison, and Johnny Cash...

. Irish guitarist The Edge was also well known for popularizing the use of slapback delay as a melodic device in the 1980s. It is also sometimes used on instruments, particularly drums
Drum kit
A drum kit is a collection of drums, cymbals and often other percussion instruments, such as cowbells, wood blocks, triangles, chimes, or tambourines, arranged for convenient playing by a single person ....

 and percussion
Percussion instrument
A percussion instrument is any object which produces a sound when hit with an implement or when it is shaken, rubbed, scraped, or otherwise acted upon in a way that sets the object into vibration...

. Slapback was often produced by refeeding the output signal from the playback head of a tape recorder to its record head, the physical space between heads, the speed of the tape, and the chosen volume being the main controlling factors. Analog and later digital delay machines also easily produced the effect.

Flanging is an audio effect produced by mixing two identical signals together, with one signal delayed by a small and gradually changing period, usually smaller than 20 milliseconds. This produces a swept comb filter effect: peaks and notches are produced in the resultant frequency spectrum,...

, chorus
Chorus effect
In music, a chorus effect occurs when individual sounds with roughly the same timbre and nearly the same pitch converge and are perceived as one...

and reverberation
Reverberation is the persistence of sound in a particular space after the original sound is removed. A reverberation, or reverb, is created when a sound is produced in an enclosed space causing a large number of echoes to build up and then slowly decay as the sound is absorbed by the walls and air...

(reverb) are all delay-based sound effects. With flanging and chorus, the delay time is very short and usually modulated. With reverberation there are multiple delays and feedback so that individual echoes are blurred together, recreating the sound of an acoustic space.

Straight delay

In sound reinforcement system
Sound reinforcement system
A sound reinforcement system is the combination of microphones, signal processors, amplifiers, and loudspeakers that makes live or pre-recorded sounds louder and may also distribute those sounds to a larger or more distant audience...

s, a straight delay is used to compensate for the passage of sound through the air. Unlike audio delay effects devices, straight delay is not mixed back in with the original signal. The delayed signal alone is sent to loudspeakers so that the speakers reinforce the stage sound at the same time or slightly later than the acoustic sound from the stage, approximately 1 millisecond of straight delay per foot of air or 3 milliseconds per meter, depending on the air temperature's effect on the speed of sound
Speed of sound
The speed of sound is the distance travelled during a unit of time by a sound wave propagating through an elastic medium. In dry air at , the speed of sound is . This is , or about one kilometer in three seconds or approximately one mile in five seconds....

. Because of the Haas effect
Haas effect
The Haas effect is a psychoacoustic effect, described in 1949 by Helmut Haas in his Ph.D. thesis. It is often equated with the underlying precedence effect .- Experiments and findings :...

, this technique allows audio engineers to use additional speaker systems placed away from the stage and still give the illusion that all sound originates from the stage. The purpose is to deliver sufficient sound volume to the back of the venue without resorting to excessive sound volumes near the front.

Straight delay is also used in audio to video synchronization
Audio to video synchronization
Audio to video synchronization refers to the relative timing of audio and video parts during creation, post-production , transmission, reception and play-back processing...

 to align sound with visual media if the visual source is delayed. Visual media can become delayed by a number of mechanisms, in which case the associated audio should be delayed to match.

See also

  • Broadcast delay
    Broadcast delay
    In radio and television, broadcast delay refers to the practice of intentionally delaying broadcast of live material. A short delay is often used to prevent profanity, bloopers, violence, or other undesirable material from making it to air, including more mundane problems such as technical...

     — other analog and digital implementations of delay for radio and television broadcasting
  • Chorus (audio effect)
    Chorus effect
    In music, a chorus effect occurs when individual sounds with roughly the same timbre and nearly the same pitch converge and are perceived as one...

  • Echo machine
    Echo machine
    An echo machine is the early name for a sound processing device used with electronic instruments to repeat the sound and produce a simulated echo. The device was popular with guitarists and was used by Brian May, Jimmy Page and Syd Barrett among others. Nowadays it would normally be called a Delay...

     — early equipment
  • Flanging
    Flanging is an audio effect produced by mixing two identical signals together, with one signal delayed by a small and gradually changing period, usually smaller than 20 milliseconds. This produces a swept comb filter effect: peaks and notches are produced in the resultant frequency spectrum,...


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