Rhythm Changes: The Jazz Musician's Second Language
If the 12-bar blues is the mother tongue of jazz, then rhythm changes is its second language — a harmonic dialect so deeply embedded in the tradition that every serious jazz musician must master it. Derived from George Gershwin's 1930 Broadway hit "I Got Rhythm," this 32-bar chord progression has served as the foundation for hundreds of jazz compositions, from the swing era through bebop and beyond.
The Origins: Gershwin's Gift to Jazz
Gershwin composed "I Got Rhythm" for the 1930 musical Girl Crazy, and within a decade the song's chord changes had taken on a life entirely their own. The earliest known use of the progression in jazz was Sidney Bechet's 1932 recording of "Shag." By the 1940s, bebop musicians had fully adopted the changes as a creative canvas.
Practically speaking, writing a new melody over existing chord changes — a contrafact — allowed musicians to claim copyright without paying royalties to Gershwin's estate. Artistically, the progression offered a rich harmonic landscape: a brisk I–vi–ii–V cycle in the A sections and a dramatic circle-of-fifths bridge.
Anatomy of the Progression
Rhythm changes follows a 32-bar AABA form. The progression is most commonly performed in B♭ major.
| Bars | Chord Function | Typical Chords (B♭) | |------|----------------|---------------------| | 1–2 | I – vi – ii – V | B♭6 – Gm7 – Cm7 – F7 | | 3–4 | I – vi – ii – V | B♭6 – Gm7 – Cm7 – F7 | | 5 | I – I7 | B♭6 – B♭7 | | 6 | IV – iv | E♭maj7 – E♭m7 | | 7–8 | I – V – I | B♭6 – F7 – B♭6 |