Also known as bebop, bop was a radical new music that developed gradually in the early 1940's and seemed to explode in 1945. The main difference between bop and swing is that the soloists engaged in chordal (rather than melodic) improvisation, often discarding the melody altogether after the first chorus and using the chords as the basis for the solo. Ensembles tended to be unisons, most jazz groups were under seven pieces and the soloist was free to get as adventurous as possible as long as the overall improvisation fit into the chord structure. Since the musicians were getting away from using the melodies as the basis for their solos (leading some listeners to ask "Where's the melody?"), the players were generally virtuosos and some of the tempos were very fast, bop divorced itself during the early years of bop from popular music and a dancing audience, uplifting jazz to an art music but cutting deeply into its potential commercial success. Ironically the once-radical bebop style has become the foundation for all of the innovations that followed and now can be almost thought of as establishment music. Among its key innovators were altoist Charlie Parker, trumpeter Dizzy Gillespie, pianist Bud Powell, drummer Max Roach and pianist-composer Thelonious Monk. Bop also mutated into Swing-Bop, which crossed the inventions of bop with a swinging Big Band, and Vocalese, which was a vocal interpretation of bop. Contemporary artists performing straight bop are often classified as Modern Bop

(All Music Guide)