“The term "chorus form" is often used to denote a type of performance - typically in jazz or rhythm 'n' blues, but also sometimes in country music and rock 'n' roll - where a given structural unit is repeated an indefinite number of times. The unit itself may be sectionally elaborate, as in the case of most Tin Pan Alley ballads. It may be twelve-bar blues, or something similar, as in the case of many R&B and rock 'n' roll numbers: here, a three-line AAB lyric, set to a three-phrase melody, is underpinned by a single gestural sweep in the harmony. Occasionally - as in some funk, dub reggae, and hip-hop, for example - it may approach the status of open-ended process.”

[Key Terms in Popular Music and Culture, ISBN 0631212639, Middleton, Richard, 1999]