Jazz improvisation
Accompaniment
Accompaniment
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In jazz, when one instrumentalist or singer is doing a solo, the other ensemble members play [accompaniment](/wiki/Accompaniment "Accompaniment") parts. While fully written\-out accompaniment parts are used in large jazz ensembles, such as [big bands](/wiki/Big_band "Big band"), in small groups (e.g., [jazz quartet](/wiki/Jazz_quartet "Jazz quartet"), [piano trio](/wiki/Piano_trio "Piano trio"), [organ trio](/wiki/Organ_trio "Organ trio"), etc.), the [rhythm section](/wiki/Rhythm_section "Rhythm section") members typically improvise their accompaniment parts, an activity called *[comping](/wiki/Comping_%28jazz%29 "Comping (jazz)")*. In jazz, the instruments in the rhythm section depend on the type of group, but they usually include a bass instrument ([double bass](/wiki/Double_bass "Double bass"), [electric bass](/wiki/Electric_bass "Electric bass")), one or more instruments capable of playing [chords](/wiki/Chord_%28music%29 "Chord (music)") (e.g., [piano](/wiki/Piano "Piano"), [electric guitar](/wiki/Electric_guitar "Electric guitar")) and [drum kit](/wiki/Drum_kit "Drum kit"). Some ensembles may use different instruments in these roles. For example, a 1920s\-style [Dixieland jazz](/wiki/Dixieland_jazz "Dixieland jazz") band may use [tuba](/wiki/Tuba "Tuba") as a bass instrument and [banjo](/wiki/Banjo "Banjo") as the chordal instrument. A 1980s\-era [jazz\-rock fusion band](/wiki/Fusion_jazz "Fusion jazz") may use [synth bass](/wiki/Synth_bass "Synth bass") for the [bassline](/wiki/Bassline "Bassline") and a [synthesizer](/wiki/Synthesizer "Synthesizer") for chords. Some bands add one or more [percussionists](/wiki/Percussionist "Percussionist").

In small groups, the rhythm section members typically improvise their accompaniment parts. Bass instrument players improvise a bassline using the [chord progression](/wiki/Chord_progression "Chord progression") of the key as a guide. Common styles of bass comping parts include a [walking bassline](/wiki/Walking_bass "Walking bass") for 1920s\-1950s jazz; rock\-style [ostinato](/wiki/Ostinato "Ostinato") riffs for jazz\-rock fusion; and Latin basslines for [Latin jazz](/wiki/Latin_jazz "Latin jazz"). Improvised basslines typically outline the harmony of each chord by playing the root, third, fifth and seventh of each chord, and playing any other notes that the composer has requested in the chord (e.g., if the chord chart indicates a [sixth chord](/wiki/Sixth_chord "Sixth chord") on the tonic in C Major, the bassist might include the sixth degree of the C Major scale, an "A" note, in their bassline).

The chordal instrument players improvise chords based on the chord progression. Chordal instrument players use jazz [chord voicings](/wiki/Chord_voicing "Chord voicing") that are different from those used in [popular music](/wiki/Popular_music "Popular music") and [classical music](/wiki/Classical_music "Classical music") from the [common practice period](/wiki/Common_practice_period "Common practice period"). For example, if a pop musician or one from the [Baroque music](/wiki/Baroque_music "Baroque music") era (ca. 1600\-1750\) were asked to play a [dominant seventh](/wiki/Dominant_seventh "Dominant seventh") chord in the key of C Major, they would probably play a root position chord named G7 (or "G dominant seventh"), which consists of the notes G, B, D and F, which are the root, third, fifth and flat seventh of the G chord. A post\-Bebop era jazz player who was asked to play a [dominant seventh](/wiki/Dominant_seventh "Dominant seventh") chord in the key of C Major might play an [altered dominant](/wiki/Altered_dominant "Altered dominant") chord built on G. An altered dominant contains flattened or sharpened "extensions" in addition to the basic elements of the chord. As well, in jazz, chordal musicians often omit the root, as this role is given to the bass player. The fifth of the chord is often omitted as well, if it is a [perfect fifth](/wiki/Perfect_fifth "Perfect fifth") above the root (as is the case in regular [major chords](/wiki/Major_chord "Major chord") and [minor chords](/wiki/Minor_chord "Minor chord")).

The altered extensions played by a [jazz guitarist](/wiki/Jazz_guitar "Jazz guitar") or [jazz pianist](/wiki/Jazz_piano "Jazz piano") on an altered dominant chord on G might include (at the discretion of the performer) a flatted [ninth](/wiki/Ninth "Ninth") A (a ninth scale degree flattened by one semitone); a sharp [eleventh](/wiki/Eleventh "Eleventh") C (an eleventh scale degree raised by one semitone) and a flattened [thirteenth](/wiki/Thirteenth "Thirteenth") E (a thirteenth scale degree lowered by one semitone). If the chordal playing musician were to omit the root and fifth of the dominant seventh chord (the G and D) and keep the third (B) and flatted seventh (F), and add the altered tones just listed (A, C and E), the resulting chord would be the pitches B, C, E, F, A, which is a much different\-sounding chord than the standard G7 played by a pop musician (G, B, D, F). In Classical harmony and in pop music, chord voicings often double the root to emphasize the foundation of the chord progression.


What instruments play chords based on the chord progression?