A form of jazz developed in the early and mid-1940s characterised by fast tempos and improvisation based on harmonic structure rather than melody.
The young boppers began to develop their own style out of the swing music of the 1930s. Musicians including Dizzy Gillespie, Charlie Parker, Bud Powell and Thelonious Monk were influenced by adventurous soloists of the preceding generation, such as pianist Art Tatum, tenor saxophonists Coleman Hawkins and Lester Young, and the trumpet player Roy Eldridge. Gillespie and Parker had travelled with some of the pre-bop masters, including Jack Teagarden, Earl Hines and Jay McShann. These musicians had begun exploring more advanced harmonies, complex syncopation, altered chords, and chord substitutions, and the boppers continued this exploration with more freedom and a purposefully arcane approach.
Early bebop players included the Benny Goodman Orchestra's guitarist, Charlie Christian, who had already hinted at the bop style in innovative solos with Goodman's band, while the pianist Thelonious Monk's personality epitomised the hip counter-cultural element of bop style. Monk's original compositions comprise one of the first bodies of work written for bebop, making him one of the form's most highly regarded contributors.
Freed from the demands of the big band arrangement, bebop quartets, quintets and sextets allowed close communication which facilitated free flowing improvisation by all the musicians, a new direction for jazz. It was not essentially for dancing, but for listening. With the steady swing held tight by a bassist, drummers began to improvise more with their left hands on snare and right foot on bass. Max Roach, Philly Joe Jones, Roy Haynes and Kenny Clarke began to support and respond to soloists, almost like a shifting call and response, using rhythmic accent to create another layer of music. This style of drumming has its roots in the second-line drumming of early 20th and late 19th century marching bands. Bebop lost listeners with tempos too hot for dancers and melodies that sounded incoherent to the untrained ear.
The classic bebop combo consisted of saxophone, trumpet, bass, drums and piano. This was a format used and popularised by both Charlie Parker (alto sax) and Dizzy Gillespie (trumpet) in their 1940s groups and recordings, sometimes augmented by an extra saxophonist or guitar, occasionally adding other horns (often a trombone) or other strings (usually fiddle or violin) or dropping an instrument and leaving only a quartet.
By the mid-1950s, musicians such as Miles Davis and John Coltrane were beginning to explore directions beyond the standard bebop vocabulary. Simultaneously, other players expanded on the bold steps of bebop with cool jazz or west coast jazz, as well as free jazz and avant-garde forms.
Bebop style also influenced the beatniks whose spoken-word style drew on jazz rhythms, and who often employed jazz musicians to accompany them, as well as rock and roll, which contains solos employing a similar form as bop solos, and hippies, who, like the boppers had a unique, non-conformist style of dress, a vocabulary incoherent to outsiders, a communion through music, and an idea of being hip or cool. Fans of bebop were not restricted to the USA and the music gained cult status in France and Japan.
Although only one part of a rich jazz tradition, bebop music continues to be played regularly throughout the world. Trends in improvisation since its era have changed from its harmonically-tethered style, but the capacity to improvise over a complex sequence of altered chords is a fundamental part of any jazz education. Bebop requires a mathematical and problem-solving mental agility, leading mastery of this language to be something of a requisite rite of passage for serious musicians.