Rhythm changes

In jazz and jazz harmony, "rhythm changes" refers to the chord progression occurring in George Gershwin's song "I Got Rhythm". This pattern, which forms the basis of countless (usually uptempo) jazz compositions, was popular with swing-era 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", "Charlie Parker'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 extremely common in the '40s and '50s, and are now ubiquitous. First, "I Got Rhythm" was by then already a popular jazz standard, and by listening to the song and writing a new melody over its chord changes (a type of composition known as a contrafact), a jazz musician could claim copyright to the new melody rather than acknowledge Gershwin's inspiration and pay royalties to his estate.

In popular music, "rhythm changes" refers to the first four-chord section of the full progression that the term denotes in the jazz context. This "sub-progression" forms the entire harmonic structure of an enormous number of popular hits released during the 1950s and 1960s (as well as of a significant number since then), in part because Gershwin's song is not the only source of this portion of the progression: Because the chord changes in question form part of a circle progression, they have been readily amenable to independent discovery by other artists both before and after Gershwin, with the effect that less creative musicians have been able to "borrow" the progression from songs other than "I Got Rhythm" whether or not those songs themselves borrowed from Gershwin.

Today, mastery of the blues and rhythm changes are "critical elements for building a jazz repertoire".

David Yaffe argues that the use by African-American musicians and groups of a chord structure written by a Jewish musician is a highly visible example of the collaboration between the groups that took place in song more than in written literature due to racial segregation.

Structure

Rhythm changes A section in C .

Rhythm changes complete in C .

The "rhythm changes" is a thirty-two-bar AABA form containing four eight measure sections. In roman numeral shorthand, the actual chords used in the "A" section are

| I vi  | ii V | 

(tonic-submediant-supertonic-dominant) played twice, then

| I I7  | IV #ivdim7 | I V | I |  (or
| I I7  | IV  iv     |             which is what Gershwin originally wrote) 

In C major, for example, these chords would be

| C Am7 | Dm G     | C Am7 | Dm G  |
| C C7  | F  F#dim | C G   | C     |  (or
| C C7  | F  Fm    |                     )

Rhythm changes bridge in C .

The "bridge" consists of a series of dominant sevenths that follow the circle of fifths, sustained for two bars each and thus conveying the sense of a shifting key center:

| III7  |   +   | VI7   |   +   |
| II7   |   +   | V7    |   +   |

In our example, we begin with an E7, followed by an A7, then D7 and finally G7, bringing us back to the original key for a final reprise of the A section. A two-bar "tag" at the end of the Gershwin tune is generally omitted. While rhythm changes can be played in any key, they are most commonly played in concert B-flat and sometimes E-flat.

Variant versions of the A section changes are legion: often the beboppers, for instance, would superimpose series of "two-fives" (passing sequences of minor-7th and dominant-7th chords) on the A section in order to make things interesting for themselves (and in order to discourage lesser musicians from sitting in on the bandstand).

Frank Vignola provides the following variants, for example:

| C Am7   | Dm7 G7   |

| C C#dim | Dm7 G7b9 |

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" 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. Often in rhythm changes tunes, the B section is left free for improvisation even during the head (e.g. in Sonny Rollins' "Oleo").

Examples

The following is a partial list of songs based possibly in part on Rhythm Changes, although there is some debate to how accurate this list is, as many of these songs uses significantly different chord changes:

• "Anthropology" (Charlie Parker/Dizzy Gillespie)
• "Cotton Tail" (Duke Ellington)
• "Dexterity" (Charlie Parker)
• "Fingers" (Thad Jones)
• "Five Guys Named Mo" (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)
• "Rhythm-A-Ning" (Thelonious Monk)
• "The Sheriff" (John Lewis)
• "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)