With the exception of the blues, the rhythm changes progression is probably the mostimportant chord progression in jazz. The term “rhythm changes” refers to a 32-bar AABAform based on the harmonic structure of “I Got Rhythm” by George and Ira Gershwin.The song appeared in the Aarons and Freedley production Girl Crazy (1930) andoriginally featured a 34-bar AABA form with a two-bar extension in the last A section.The two-bar extension was eventually cut and the chord changes of the last A sectionreplicated those from the second A. A newly composed line based on the rhythm changesprogression is known as a contrafact. The enormous popularity of rhythm changes hasbeen well documented by an ever-increasing number of composed contrafacts andrecordings

Charlie Parker wrote a number of contrafacts on rhythm changes among which “Moosethe Mooche,” shown in Figure 19.1, is one of the most well known

Chapter 22 undertakes a study of song forms and its most common type: the 32-barAABA. Two tonal variants, on-tonic and off-tonic, are examined and, as an example ofthe on-tonic AABA formal design, “Have You Met Miss Jones?” is analyzed.

The AABA Song Form