Definition
The rhythm changes are the chord progression of I Got Rhythm by George and Ira Gershwin (1930), which became, after the blues, the most used form in jazz. 32-bar AABA form, home key Bb. Hundreds of new melodies (contrafacts) have been written over these chords: Anthropology (Parker/Gillespie), Oleo (Sonny Rollins), Moose the Mooche (Parker), Cotton Tail (Ellington), Rhythm-a-Ning (Monk), Lester Leaps In (Lester Young); even the Flintstones theme uses them.
The A section (8 bars, Bb)
Basic version:
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 |
|---|---|---|---|---|---|---|---|
| Bb G7 | Cm7 F7 | Bb G7 | Cm7 F7 | Bb Bb7 | Eb Edim7 | Bb/F F7 | Bb (Cm7 F7) |
| I VI7 | ii V | I VI7 | ii V | I I7 | IV #iv°7 | I/5 V7 | I |
- Bars 1–4: two I–vi–ii–V turnarounds (with VI7 = V/ii).
- Bar 5: Bb7 = V/IV, tonicizes Eb.
- Bar 6: #iv°7 passing diminished toward Bb/F.
- Bars 7–8: cadence.
The bridge (8 bars)
| 9–10 | 11–12 | 13–14 | 15–16 |
|---|---|---|---|
| D7 | G7 | C7 | F7 |
| III7 | VI7 | II7 | V7 |
A chain of dominants by fifths, each lasting 2 bars (the so-called "Sears Roebuck bridge" in musicians' slang).
Bebop variants of the A
- Turnaround with iii: | Dm7 G7 | Cm7 F7 |
- Bars 5–6 with ii–V: | Fm7 Bb7 | Ebmaj7 Ab7 | (Ab7 is the minor IV/backdoor of Bb)
- Bars 5–8 with chains: | Fm7 Bb7 | Eb7 Ab7 | Dm7 G7 | Cm7 F7 |
- Tritone substitutions: | Bb Db7 | Cm7 B7 | (bass Bb – Db – C – B: Db7 substitutes for G7, B7 substitutes for F7)
Bridge variants
- With related ii chords: | Am7 D7 | Dm7 G7 | Gm7 C7 | Cm7 F7 |
- With subV: | D7 Ab7 | G7 Db7 | C7 Gb7 | F7 B7 |
- With Coltrane changes (modern) or with an F pedal for the whole bridge.
How it is played
- Tempo: from medium-fast to very fast (200–300 BPM is common in bebop).
- On the A sections you think in terms of tonal center (Bb major with blue notes) more than chord by chord.
- On the bridge you play the guide tones of the dominants: F# – C, F – B, E – Bb, Eb – A (thirds and sevenths of D7, G7, C7, F7).
- The bass in the A walks with chromatic approaches; on the bridge it emphasizes the roots.
Historical notes
In Gershwin's original version the final A had 2 extra bars (a "tag"): jazz normalized it to 8 bars. The spread of rhythm changes in the 1940s is tied to the jam sessions at Minton's and the development of bebop.
Exercise for the producer
- Program a walking bass (sampled upright bass) over the rhythm changes at 180 BPM, one quarter note per note.
- Add piano comping with shell voicings (root, 3, 7).
- Compose a new 8-bar melody on the A: your first contrafact.
Related topics
The ii–V–I in jazz, secondary dominants, passing diminished chords, jazz standards and harmonic forms, Bird blues.