Unison
Encyclopedia
In music
Music
Music is an art form whose medium is sound and silence. Its common elements are pitch , rhythm , dynamics, and the sonic qualities of timbre and texture...

, the word unison can be applied in more than one way. In general terms, it may refer to two notes sounding the same pitch, often but not always at the same time; or to the same musical voice being sounded by several voices or instruments together, either at the same pitch or at a distance of one or more 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"...

s; or to rhythmic patterns which are homorhythmic.

Interval of the unison

Unison (also called a "prime") may refer to the (pseudo-)interval
Interval (music)
In music theory, an interval is a combination of two notes, or the ratio between their frequencies. Two-note combinations are also called dyads...

 formed by a tone and its duplication (in German, Unisono, Einklang, or Prime), for example C–C, as differentiated from the second
Major second
In Western music theory, a major second is a musical interval spanning two semitones, and encompassing two adjacent staff positions . For example, the interval from C to D is a major second, as the note D lies two semitones above C, and the two notes are notated on adjacent staff postions...

, C–D, etc. In the unison the two pitches have the ratio of 1:1 or 0 half step
Minor second
In modern Western tonal music theory a minor second is the interval between two notes on adjacent staff positions, or having adjacent note letters, whose alterations cause them to be one semitone or half-step apart, such as B and C or C and D....

s and zero cents
Cent (music)
The cent is a logarithmic unit of measure used for musical intervals. Twelve-tone equal temperament divides the octave into 12 semitones of 100 cents each...

. Although two tones in unison are considered to be the same pitch, they are still perceivable as coming from separate sources, whether played on instruments of a different type: ; or of the same type: . This is because a pair of tones in unison come from different locations and/or can have different "colors" (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...

s), i.e. come from different musical instrument
Musical instrument
A musical instrument is a device created or adapted for the purpose of making musical sounds. In principle, any object that produces sound can serve as a musical instrument—it is through purpose that the object becomes a musical instrument. The history of musical instruments dates back to the...

s or human voices. Voices with different colors have, as sound waves, different waveform
Waveform
Waveform means the shape and form of a signal such as a wave moving in a physical medium or an abstract representation.In many cases the medium in which the wave is being propagated does not permit a direct visual image of the form. In these cases, the term 'waveform' refers to the shape of a graph...

s. These waveforms have the same fundamental frequency
Frequency
Frequency is the number of occurrences of a repeating event per unit time. It is also referred to as temporal frequency.The period is the duration of one cycle in a repeating event, so the period is the reciprocal of the frequency...

 but differ in the amplitudes of their higher harmonic
Harmonic
A harmonic of a wave is a component frequency of the signal that is an integer multiple of the fundamental frequency, i.e. if the fundamental frequency is f, the harmonics have frequencies 2f, 3f, 4f, . . . etc. The harmonics have the property that they are all periodic at the fundamental...

s. The unison is considered the most consonant interval while the near unison
Minor second
In modern Western tonal music theory a minor second is the interval between two notes on adjacent staff positions, or having adjacent note letters, whose alterations cause them to be one semitone or half-step apart, such as B and C or C and D....

 is considered the most dissonant. The unison is also the easiest interval to tune
Musical tuning
In music, there are two common meanings for tuning:* Tuning practice, the act of tuning an instrument or voice.* Tuning systems, the various systems of pitches used to tune an instrument, and their theoretical bases.-Tuning practice:...

. The unison is abbreviated as P1.

However, the unison was questioned by Zarlino
Gioseffo Zarlino
Gioseffo Zarlino was an Italian music theorist and composer of the Renaissance. He was possibly the most famous music theorist between Aristoxenus and Rameau, and made a large contribution to the theory of counterpoint as well as to musical tuning.-Life:Zarlino was born in Chioggia, near Venice...

 as an interval for lacking contrast and compared to a point
Point (geometry)
In geometry, topology and related branches of mathematics a spatial point is a primitive notion upon which other concepts may be defined. In geometry, points are zero-dimensional; i.e., they do not have volume, area, length, or any other higher-dimensional analogue. In branches of mathematics...

 in geometry:

"In unison"

In orchestral music unison can mean the simultaneous playing of a note (or a series of notes constituting a melody
Melody
A melody , also tune, voice, or line, is a linear succession of musical tones which is perceived as a single entity...

) by different instruments, either at the same 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,...

; or in a different 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"...

, for example, cello
Cello
The cello is a bowed string instrument with four strings tuned in perfect fifths. It is a member of the violin family of musical instruments, which also includes the violin, viola, and double bass. Old forms of the instrument in the Baroque era are baryton and viol .A person who plays a cello is...

 and double bass
Double bass
The double bass, also called the string bass, upright bass, standup bass or contrabass, is the largest and lowest-pitched bowed string instrument in the modern symphony orchestra, with strings usually tuned to E1, A1, D2 and G2...

 (all'unisono). Typically a section string player plays unison with the rest of the section. Occasionally the Italian word divisi (meaning divided, abbrev. div.) marks a point where an instrumental section, typically the first violins, is to be divided into two groups for rendering passages that might, for example, include full chords
Chord (music)
A chord in music is any harmonic set of two–three or more notes that is heard as if sounding simultaneously. These need not actually be played together: arpeggios and broken chords may for many practical and theoretical purposes be understood as chords...

. Thus, in the divisi first violins the "outside" players (nearer the audience) might play the top note of the chord, while the "inside" seated players play the middle note, and the second violins play the bottom note. At the point where the first violins no longer play divisi, the score may indicate this with unison (abbrev. unis.).

When several people sing together, as in a chorus
Choir
A choir, chorale or chorus is a musical ensemble of singers. Choral music, in turn, is the music written specifically for such an ensemble to perform.A body of singers who perform together as a group is called a choir or chorus...

, the simplest way for them to sing is to sing in "one voice", in unison. If there is an instrument accompanying them, then the instrument must play the same notes being sung by the singers (in order for there to be unison). Otherwise the instrument is considered a separate "voice" and there is no unison. If there is no instrument, then the singing is said to be a cappella
A cappella
A cappella music is specifically solo or group singing without instrumental sound, or a piece intended to be performed in this way. It is the opposite of cantata, which is accompanied singing. A cappella was originally intended to differentiate between Renaissance polyphony and Baroque concertato...

. Music in which all the notes sung are in unison is called monophonic
Monophony
In music, monophony is the simplest of textures, consisting of melody without accompanying harmony. This may be realized as just one note at a time, or with the same note duplicated at the octave . If the entire melody is sung by two voices or a choir with an interval between the notes or in...

.

From this sense can be derived another, figurative
Metaphor
A metaphor is a literary figure of speech that uses an image, story or tangible thing to represent a less tangible thing or some intangible quality or idea; e.g., "Her eyes were glistening jewels." Metaphor may also be used for any rhetorical figures of speech that achieve their effects via...

, sense: if several people do something "in unison" it means they do it simultaneously, in tandem
Tandem
Tandem is an arrangement where a team of machines, animals or people are lined up one behind another, all facing in the same direction....

, in lockstep. Related terms are "univocal" and "unanimous".

Monophony could also conceivably include more than one voice which do not sing in unison but whose pitches move in parallel, always maintaining the same interval of an 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"...

. A pair of notes sung one or a multiple of an octave apart are almost in unison, due to octave equivalency.

When there are two or more voices singing different notes, this is called "part singing". If they are singing notes at different pitches but with the same rhythm this is called homophony
Homophony
In music, homophony is a texture in which two or more parts move together in harmony, the relationship between them creating chords. This is distinct from polyphony, in which parts move with rhythmic independence, and monophony, in which all parts move in parallel rhythm and pitch. A homophonic...

. An example is a barbershop quartet or a choir singing a hymn
Hymn
A hymn is a type of song, usually religious, specifically written for the purpose of praise, adoration or prayer, and typically addressed to a deity or deities, or to a prominent figure or personification...

. If each voice is singing an independent line (either the same melody at a different time, or different melodies) this is called polyphony
Polyphony
In music, polyphony is a texture consisting of two or more independent melodic voices, as opposed to music with just one voice or music with one dominant melodic voice accompanied by chords ....

.

Synthesizer

On 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, the term unison is used to describe two or more oscillators that are slightly detuned in correspondence to each other, which makes the sound fatter. This technique is so popular that some modern virtual analog synthesisers have a special oscillator type called "super saw" or "hyper saw" that generates several detuned sawtooth waves simultaneously. This method is often used in techno and trance
Trance music
Trance is a genre of electronic dance music that developed in the 1990s.:251 It is generally characterized by a tempo of between 125 and 150 bpm,:252 repeating melodic synthesizer phrases, and a musical form that builds up and breaks down throughout a track...

.

Further reading

  • Apel, Willi, ed., Harvard Dictionary of Music, Second Edition, Revised and Enlarged. The Belknap Press of Harvard University Press, Cambridge, Massachusetts, 1969. ISBN 674375017.

See also

  • Entrainment (biomusicology)
    Entrainment (biomusicology)
    Entrainment in the biomusicological sense refers to the synchronization of organisms to an external rhythm, usually produced by other organisms with whom they interact socially...

  • Entrainment (physics)
    Entrainment (physics)
    Entrainment has been used to refer to the process of mode locking of coupled driven oscillators, which is the process whereby two interacting oscillating systems, which have different periods when they function independently, assume a common period...

  • Synchronization
    Synchronization
    Synchronization is timekeeping which requires the coordination of events to operate a system in unison. The familiar conductor of an orchestra serves to keep the orchestra in time....

  • List of musical intervals
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