Rhythm changes

The Rhythm changes is a 32-bar jazz chord progression. It is started from George Gershwin's "I Got Rhythm". The progression is in AABA form. The A sections have a I–vi–ii–V chord progression (or iii–vi–ii–V). The B section goes through the circle of fifths. This is III⁷–VI⁷–II⁷–V⁷. That chord progression is sometimes given passing chords.

This pattern is very common for improvisation in jazz.^[2] It is the chord progression for many (usually fast) jazz compositions. Songs that use this chord progression are contrafacts. Rhythm changes were popular in the swing and bebop eras. It is the chord progression in Duke Ellington's song "Cotton Tail",^[3] Charlie Christian's "Seven Come Eleven,"^[4] Dizzy Gillespie's "Salt Peanuts,"^[4] and Thelonious Monk's "Rhythm-a-Ning".^[4] The first time that rhythm changes were used was by Sidney Bechet. His September 15, 1932^[5] recording of "Shag" (two years after the first performance of "I Got Rhythm" on Broadway) recording uses this chord progression. This song was recorded by his "New Orleans Feetwarmers" group.^[6]

In pop culture, "Meet the Flintstones", (c. 1960, Curtin/Hanna/Barbera) has rhythm changes.

This progression is very popular because of its use by early bebop musicians. The chord changes began to be used in the 1930s. It became more common '40s and '50s. It is now used regularly.^[7]

By the 1930s, "I Got Rhythm" was already a popular jazz standard. By listening to the song and making a melody with these chord changes, a musician could create a new song. This song would be a contrafact. The jazz musician would have copyright rights to the new melody. If they played "I Got Rhythm", they would have to pay royalties to Gershwin.

Using a popular chord progression for new melodies made it easy to play a song at a jam session, show, or recording. The new musicians would only need to know that the song has rhythm changes. They might point out any modifications or chord substitutions.

For musicians, it is important to learn both the 12-bar blues and rhythm changes.^[8]

The rhythm changes is a 32-bar AABA form. Each section has 8 bars.^[9] Using roman numerals, the chords used in the A section are:

I      vi

ii      V

I      vi

ii      V

The 2-bar phrase, I−vi−ii−V (sometimes changed to I–VI–ii–V) is played twice.^[10] Then, this is played:

I      I7

IV     iv

I      V

I

In a jazz band, these chord changes are usually played in the key of B♭.^[7] There are sometimes many chord substitutions. The next image is an example of the A section of rhythm changes, but with many common substitutions. In the 5th measure, there is a ii–V progression (Fm⁷–B♭⁷). This progression makes the IV chord (E♭) the tonic. In the 7th bar, it uses a iii−vi−ii−V chord progression instead of a I−vi−ii−V. In measures 15 and 16, it uses a ii-V-I chord progression instead of a I-V-I.

The "bridge" has many dominant seventh chords (III⁷–VI⁷–II⁷–V⁷). This progression follows the circle of fourths (ragtime progression). Each dominant seventh chord is two measures long. This section is called the Sears Roebuck bridge. It is named after Sears, Roebuck and Co.^[11]

After that, there is a final A section

There are many different versions of rhythm changes. Many people add chord substitutions, passing chords, and changes of chord quality. For example, Bebop players would often add many ii–V progressions. This was to discourage less experienced musicians from playing. The first chord was originally B♭⁶, but some people would play a B♭^M7 or B♭⁷. For example, the B section might look like this:^[12]

The following is a partial list of songs based on the rhythm changes:

• R., Ken (2012). DOG EAR Tritone Substitution for Jazz Guitar, Amazon Digital Services, ASIN: B008FRWNIW