Rhythm Changes A Section (I–VI–ii–V) in Bb

Based on Gershwin's "I Got Rhythm," this is the second most important progression in jazz after the ii–V–I. The A section in Bb: Bbmaj7–G7–Cm7–F7, repeated. The I–VI–ii–V cycle creates a fast-moving harmonic rhythm that demands quick chord changes and crisp voice-leading. Almost every bebop musician has played on Rhythm Changes.