Editing Comping (jazz) (section)

===Chords===
Comping is almost always improvised by the comping musicians based on a [[chord chart]], [[lead sheet]] (which contains the chords written above the melody), [[sheet music]], or, in [[country music]], the [[Nashville Number System]]. The exception is well-known progressions (e.g., [[12 bar blues]]) and [[jazz standard]]s such as "[[I Got Rhythm]]", known colloquially as "[[rhythm changes]]". For well-known progressions, the bandleader may simply say "solos on blues changes" or "solos on rhythm changes", and the comping musicians are expected to be familiar with these chord progressions. Top soloists playing with the most advanced comping musicians may simply call out the name of jazz standards, and the sidemen will be expected to know the chord progression. For example, the soloist may request "[[Autumn Leaves (1945 song)|Autumn Leaves]]" without providing the compers with a chord chart or sheet music. The compers at the highest professional level would be expected to know this tune.

Since there are many variant versions of these chord progressions, the comping musicians will have to come to an unspoken consensus on which chords to use. For example, there are many different [[Turnaround (music)|turnaround]]s used for the last two bars of a 12 bar blues; however, if the bandleader, playing Hammond organ, plays I/VI7/ii7/V7 for the turnaround, most skilled compers will hear these chords by ear and then replicate them in subsequent choruses (each full playing of the 12-bar progression is colloquially called a "chorus").