Rhythm changes
Rhythm changes is a common 32-bar jazz chord progression derived from George Gershwin's "I Got Rhythm". The progression is in AABA form, with each A section based on repetitions of the ubiquitous I–vi–ii–V sequence (or variants such as iii–vi–ii–V), and the B section using a circle of fifths sequence based on III7–VI7–II7–V7, a progression which is sometimes given passing chords.
This pattern, "one of the most common vehicles for improvisation," forms the basis of countless (usually uptempo) jazz compositions and was popular with swing-era and bebop musicians. For example, it is the basis of Duke Ellington's "Cotton Tail" as well as Charlie Christian's "Seven Come Eleven," Dizzy Gillespie's "Salt Peanuts," and Thelonious Monk's "Rhythm-a-Ning". The earliest known use of rhythm changes was by Sidney Bechet in his September 15, 1932 recording of "Shag" (two years after the first performance of "I Got Rhythm" on Broadway) with his "New Orleans Feetwarmers" group.