In jazz and jazz harmony, "rhythm changes" refers to the 32-bar chord progression occurring in George Gershwin's song "I Got Rhythm." The progression uses an 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 fourths 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. It is found in "Shoeshine Boy" (Lester Young's 1936 breakout recording with Count Basie) and "Cotton Tail" written by Duke Ellington in 1940, as well as Charlie Christian's "Seven Come Eleven," Dizzy Gillespie's "Salt Peanuts," and Thelonious Monk's "Rhythm-a-Ning," for instance. The earliest known use of rhythm changes was by Sidney Bechet in his September 15, 1932 recording of "Shag" with his "New Orleans Feetwarmers" group.
This progression's endurance in popularity is largely due to its extensive use by early bebop musicians. The chord changes began to be used in the 1930s, became common in the '40s and '50s, and are now ubiquitous. First, "I Got Rhythm" was by then already a popular jazz standard; second, by listening to the song and writing a new melody over its chord changes, thereby creating a composition of a type known as a contrafact, a jazz musician could claim copyright to the new melody rather than acknowledge Gershwin's inspiration and pay royalties to Gershwin's estate; third, using a stock, well-known progression for new melodies made it easier to perform a song at jam sessions, shows and recordings because the bandleader could just say to new musicians that his/her song used "rhythm changes" and note his/her modifications and chord substitutions.
The "rhythm changes" is a thirty-two-bar AABA form with each section consisting of eight bars. The four eight-measure sections. In roman numeral shorthand, the original chords used in the "A" section are
| I vi | ii V | I vi | ii V | | I I7 | IV iv | I V | I |
In a jazz band, these chord changes are usually played in the key of B♭ with various chord substitutions. Here is a typical form for the A section with various common substitutions, including VI7 in place of the minor vi chord; the addition of a ii-V progression (f minor-Bb7) that briefly tonicizes the IV chord, Eb, by preceding it with f minor and Bb7; and using iii in place of I for the final four bars of the A section, thus giving iii-VI7-ii-V in place of I-VI7-ii-V:
| B♭M7 G7 | Cm7 F7 | B♭M7 G7 | Cm7 F7 | | Fm7 B♭7 | E♭M7 A♭7 | Dm7 G7 | Cm7 F7 | | B♭M7 G7 | Cm7 F7 | B♭M7 G7 | Cm7 F7 | | Fm7 B♭7 | E♭M7 A♭7 | Cm7 F7 | B♭M7 |
The "bridge" consists of a series of dominant seventh chords that follow the circle of fourths (ragtime progression), sustained for two bars each, longer periods of each chord than the A sections, which conveys a sense of contrast:
| III7 | ⁒ | VI7 | ⁒ | | II7 | ⁒ | V7 | ⁒ | | D7 | ⁒ | G7 | ⁒ | | C7 | ⁒ | F7 | ⁒ |
The B section is then followed by the second 8 bars of the A section
| B♭M7 G7 | Cm7 F7 | B♭M7 G7 | Cm7 F7 | | Fm7 B♭7 | E♭M7 A♭7 | Cm7 F7 | B♭M7 |
Variant versions of changes are common due to the popularity of adding interest with chord substitutions, passing chords and changes of chord "quality." Bebop players, for instance, would often superimpose series of "two-fives" (passing sequences of minor seventh and dominant seventh chords) or other substitutions for interest or in order to discourage less experienced musicians from "sitting in" on the bandstand. The opening I chord was often Bb6 in Gershwin's original, but Beboppers changed it to Bb maj 7 or Bb7. The B section may appear as follows:
| Am7 | D7 | Dm7 | G7 | | Gm7 | C7 | Cm7 | F7 |
An even more adventurous Bebop-style substitution is to convert C7 /C7/F7/F7 to g min7/C7/c min7/F7, and then to further develop this substitution by changing this to a min7 D7/g min7 C7/d min7 G7/c min7 F7.
The component A and B sections of rhythm changes were also sometimes used for other tunes. For instance, Charlie Parker's "Scrapple from the Apple" and Juan Tizol's "Perdido" both use a different progression for the A section while using the Rhythm changes B section. "Scrapple from the Apple" uses the chord changes of "Honeysuckle Rose" for the A section, but replaces the B section with "Rhythm"'s III7–VI7–II7–V7 bridge. Other tunes, such as Sonny Stitt's "The Eternal Triangle" and the theme from "The Muppet Show," use the A section of "Rhythm" but have a different bridge. Tadd Dameron's "Good Bait" uses the A section of the Rhythm changes but a different progression for the bridge. Sometimes in rhythm changes tunes, the melody of the B section is left unnotated, so that the solo performer must improvise a melody, even during the head (e.g. in Sonny Rollins' "Oleo").
The following is a partial list of songs based on the rhythm changes:
- "Anthropology" (Charlie Parker/Dizzy Gillespie)
- "Cotton Tail" (Duke Ellington)
- "Dexterity" (Charlie Parker)
- "Fingers" (Thad Jones)
- "Five Guys Named Moe" (Louis Jordan and His Tympany Five)
- "Lester Leaps In" (Lester Young)
- "Little Pixie II" (Thad Jones)
- "Meet the Flintstones" (Hoyt Curtin)
- "Moose the Mooche" (Charlie Parker)
- "Oleo" (Sonny Rollins)
- ”Passport” ([[Charlie
- "Rhythm-A-Ning" (Thelonious Monk)
- "Steeplechase" (Charlie Parker)
- "Straighten Up and Fly Right" (Nat King Cole)
- "Tip Toe" (Thad Jones)
- "You, Me, and the Bottle Makes Three Tonight (Baby)" (Big Bad Voodoo Daddy)
- "Race To The Bridge" (Gordon Goodwin)
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- Dziuba, Mark (2003). The Big Book of Jazz Guitar Improvisation, p.140. ISBN 9780739031728.
- "Duke Ellington the Man and His Music", p.20. Luvenia A. George. Music Educators Journal, Vol. 85, No. 6 (May, 1999), pp. 15-21. Published by: MENC: The National Association for Music Education.
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- Rust, Brian, Jazz and Ragtime Records, 1897-1942 Archived 2009-02-09 at the Wayback Machine, Mainspring Press, 2008.
- "Rhythm Changes," MoneyChords (angelfire.com). Includes an extensive listing of tunes utilizing these chord changes.
- Spitzer, Peter (2001). Jazz Theory Handbook, p.67. ISBN 0-7866-5328-0.
- Thomas, John (2002). Voice Leading for Guitar: Moving Through the Changes, p.85. ISBN 0-634-01655-5.
- Spitzer (2001), p.68.
- Ellis, Herb and Holmes, Terry (1996). The Herb Ellis Jazz Guitar Method: Rhythm Shapes, p.4-5. ISBN 9781576233412.
- Spitzer (2001), p.81.
- Rawlins, Robert and Bahha, Nor Eddine (2005). Jazzology: The Encyclopedia of Jazz Theory for All Musicians, p.128. ISBN 9780634086786.
- Holbrook, Morris B. (2008). Playing the Changes on the Jazz Metaphor, p.104. ISBN 9781601981721.
- Spitzer (2001), p.71.
- Spitzer (2001), p.72.