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Comping (an abbreviation of accompanying) is a term used in jazz music to describe the chords, rhythms, and countermelodies that keyboard players (piano or organ) or guitar players use to support a jazz musician's improvised solo or melody lines. The term is also used for the action of accompanying, and for left hand part of a solo pianist.
The chordal accompaniment used in jazz is different from the chordal accompaniment style used in many types of popular music, such as rock and folk.
- In a rock or folk band, a guitarist or piano player will accompany by playing primarily root-position triads consisting of the notes of the chord known as the root, 3rd, and 5th. In the key of C, the G chord would include the notes G, B, and D (the root, 3rd, and 5th of the chord).
- In a jazz band a guitarist or pianist will comp by playing a variety of chords that include the notes of the chord known as the 3rd, 7th, 9th, and 13th (the bassist usually plays the root). In the key of C, the G chord might be performed by playing the notes B, E, F, and A (the 3rd, 13th, flat 7th, and 9th notes of the chord). As well, jazz compers may use altered chords that contain flattened or sharpened 5ths, 9ths, and 13ths for some songs or soloists. For example, an altered G7 chord might be played with the notes A♭, A♯, C♯, and E♭ (♭9, ♯9, ♯11, ♭13).
In combos with a guitar player, the guitar player usually comps for soloists. If there is both a pianist and a guitarist, as sometimes occurs in organ trios or big bands, they may either alternate comping or comp at the same time. Having two chordal instruments comp at the same time is difficult to do well. The two compers may make different, clashing interpretations of the same chord (e.g., the pianist may add a flat 13th, while the guitarist plays a natural 13th), or the texture may become overly cluttered.
During swing-feel songs, drummers will usually comp with one hand on the snare drum while playing time on the cymbals (see drum kit). More skilled drummers often comp with even all three limbs excluding their right-hand ride pattern (snare drum, bass drum, hi-hats). They will most likely develop the simple jazz drum pattern and add a few "bomb" bass drum notes for extra effect. In small jazz ensembles ("combos") with more unusual instrumentation, horn players (e.g., saxophone, trumpet, etc.) can comp by playing the melody line in the background, or by playing a sequence of notes called "guide tones" which outline the harmonic framework. Guide tones are usually the 3rd, 7th, or 9th notes of a given chord. Guide tone lines are constructed by descending through the guide tones of the chart, normally by semitone. For instance, in a duo for saxophone and bass, the saxophonist will usually comp during the bass solo by playing guide tones.
During a drum solo the pianist sometimes comps, often using a predictable pattern of rhythmically-played chords called "hits". A well-known example is the second half of "Take Five", with Dave Brubeck's piano vamp comping for Joe Morello's drum solo. During piano solos, pianists often comp for themselves, playing melodic lines and solos with the right hand while comping with the left hand.
Roles of a comping musician 
While any jazz instrument can be used for comping, the chordal rhythm section instruments (piano, organ, and guitar) have developed the largest collection of pedagogical materials about comping. Since a jazz solo has such wide ranging harmonic, melodic, and rhythmic possibilities, chordal instruments must have a similarly wide range of tools at their disposal to support the soloist properly. Comping musicians must know many different types of chord voicings so that they can match the mood the soloist is trying to create. To support some soloists, a comper needs to use very simple voicings (such as the 3rd and 7th of a chord). However, for other soloists who play in a very dense, complicated style, compers may need to use chords with many additional extensions, such as 9ths, 13ths, and altered voicings; they may also re-harmonize chord progressions depending on the soloist, thus creating a feedback of idea exchange between the soloist and the comper. Compers must have an understanding of rhythm that allows them to respond to the rhythms the soloist plays, such as Latin or Afro-Cuban rhythms. As well, they must have a melodic sense based on a knowledge of a huge repertoire of different scales and scalar patterns, to be able to improvise countermelodies to supplement the soloist's melodies and fill in empty spaces. By comping, pianists, organists, and guitarists provide the "glue" that holds the rhythm section together. They take the soloist's improvised solos and melodies and add harmonies (as a bass player does) and rhythms (as a drummer does). By doing this, the comper helps ensure that the band is always at the same energy level as the soloist. Wynton Kelly and Herbie Hancock are examples of pianists who are responsive when comping. Oscar Peterson usually comped busily, while Count Basie comped sparsely. There is no single appropriate way to comp for a soloist.
See also 
- Chord chart
- Organ trios, a type of ensemble which poses particular comping challenges, since there are usually two chordal instruments which have to share the accompanying tasks (e.g., Hammond organ and guitar)
Further reading 
- Green, Andrew (2005). Jazz Guitar Comping. ISBN 0-9700576-4-4.
- Hughes (2002), p.6.
- Hughes, Fred (2002). The Jazz Pianist: Left Hand Voicings and Chord Theory, p.5. ISBN 9780757993152.