The early 1940s saw the development of bebop, a complex style of music usually for small jazz groups consisting of four to six players. In part, bebop was a rebellion by creative improvisers against the commercialism and written arrangements of swing bands. The new music was meant for attentive listening, not dancing and its sophisticated harmonies and unpredictable rhythms bewildered many listeners. Bebop performers were a special “in” group who sometime drove other jazz musicians from the bandstand by using complex melodies and unusual chord progressions. “We knew that they couldn’t make those chord changes”, one bebop drummer recalled. “We kept the riffraff out and built our clique on new chords”. Bebop performers also differentiated themselves by their goatees, berets, and special “hip” language.

A typical bebop group might include a saxophone and a trumpet supported by a rhythm section of piano, bass and percussion. The role of the rhythm instruments in bebop was different from that in earlier jazz. The beat, often extremely fast, was not marked by the snare or bass drum, but mainly by the pizzicato bass and ride cymbal. The drummer also supplied irregular accents, sometimes played with such power that they were called “bombs”. Similarly, the pianist’s left hand no longer helped emphasize the basic pulse but joined with the right hand to play complex chords at irregular intervals.

Rhythms in bebop melodies were more varied and unpredictable than those in earlier jazz. These melodies often had a flurry of extremely fast notes with accents on the offbeats. The harmonies of bebop were as complex as its rhythms. Performers often built melodies on chords consisting of five to seven notes rather than on the three or four note chords used in earlier jazz.

A bebop performance generally began and ended with a statement of the main theme by one of the soloists, or by two soloists in unison. The remainder of the piece was made up of solo improvisations based on the melody or harmonic structure. As in earlier jazz, bebop musicians used popular songs and 12-bar blues as a springboard for improvisation. Often, however, they composed new tunes to fit the basic harmonies of familiar melodies. As an “in” joke, a bebop musician might give a tune a new title so that only sophisticated listeners could guess its origin. This is called contrafacting.