Rhythm Changes
The 32-bar AABA form behind a thousand bebop heads · A: I – vi – ii – V · B: III7 – VI7 – II7 – V7
Rhythm Changes is, after the 12-bar blues, the second-most-played form in jazz. It is a 32-bar AABA structure: the A sections cycle through a fast I–vi–ii–V loop around the tonic, and the B section (the bridge) climbs through a chain of dominant chords — III7–VI7–II7–V7 — before dropping back into the final A. Hundreds of bebop tunes were written over this exact harmonic frame because every working jazz musician already knows the changes, so a new melody is all it takes to make a new piece. (The form is named for the public-domain harmonic structure; the original tune's melody is not reproduced here.)
The A section — I, vi, ii, V cycling
Two bars of I – vi – ii – V, twice. The rapid, tonic-anchored loop that makes up three-quarters of the 32-bar form. Try it in B♭ — the traditional key for Rhythm Changes — or any other.
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The burnt sienna palette on this page is inspired by music-color synesthesia — rhythm changes maps to burnt sienna, reflecting its driving, up-tempo swing.
About Rhythm Changes
Rhythm Changes takes its name from the chord changes to George Gershwin's 1930 song "I Got Rhythm." The harmonic structure — not the melody — entered the public jazz vocabulary, and musicians began composing new tunes over it. The form is 32 bars in AABA shape: three eight-bar A sections and one eight-bar bridge (the B). The traditional key is B♭. Because the form is so universally known, it functions like the 12-bar blues — a shared frame any group of players can perform together without rehearsal, with each player's solo built on the same well-worn changes.
The A section is anchored firmly on the tonic and cycles through a fast I – vi – ii – V turnaround, often two chords per bar. That turnaround — tonic, relative minor, supertonic, dominant — is itself one of the most common progressions in all of jazz, and Rhythm Changes essentially repeats it for sixteen of the form's thirty-two bars. The relentless I–vi–ii–V motion gives the A sections their characteristic forward drive and gives soloists a stable, predictable harmonic bed to spin fast bebop lines over. Bars 5–6 typically move to IV (and sometimes a iv or ♯IV°) for contrast before the turnaround pulls everything back to I.
The bridge is where Rhythm Changes becomes a harmony lesson. Instead of staying in the home key, it climbs through a "cycle of dominants": III7 – VI7 – II7 – V7, with each dominant chord typically held for two bars. In B♭ that is D7 – G7 – C7 – F7 — a chain of dominant sevenths each resolving to the next by descending fifth, walking the music through several keys before the final V7 drops it back into the last A section. This dominant-cycle bridge is so distinctive that jazz musicians call any similar passage "rhythm bridge" changes, and learning to navigate it is a core skill for bebop improvisation.
The list of tunes built on Rhythm Changes is enormous. Charlie Parker's "Anthropology" and Sonny Rollins's "Oleo" are the canonical bebop heads; Duke Ellington's "Cotton Tail" and Lester Young's feature "Lester Leaps In" are swing-era classics on the same form. The reason so many composers reached for it is practical: writing a melody over Rhythm Changes instantly produces a tune the whole jazz community can already play. For a student, the payoff is the same in reverse — learn Rhythm Changes once and you can sit in on dozens of standards, because they all share these thirty-two bars.
Variations
The bridge — III7, VI7, II7, V7
The "cycle of dominants" B section. Four dominant sevenths descending by fifths through several keys and back home.
The turnaround — I, VI7, ii7, V7
The cadence that closes each A section, with a dominant VI7 as a secondary dominant pulling into ii.
Famous songs & pieces
- I Got Rhythm — George Gershwin (The 1930 song whose changes define the form)
- Oleo — Sonny Rollins (A canonical bebop head on Rhythm Changes)
- Anthropology — Charlie Parker & Dizzy Gillespie (Bebop melody over the AABA form)
- Cotton Tail — Duke Ellington (A swing-era classic on Rhythm Changes)
- Lester Leaps In — Lester Young (Count Basie small-group feature on the form)
- Oleo / Moose the Mooche / Rhythm-a-ning — Various (Dozens of jazz standards share these changes)