In the early 1940s in jazz, bebop emerged, led by Charlie Parker, Dizzy Gillespie, Thelonious Monk and others. It helped to shift jazz from danceable popular music towards a more challenging "musician's music." Differing greatly from swing, early bebop divorced itself from dance music, establishing itself more as an art form but lessening its potential popular and commercial value. Since bebop was meant to be listened to, not danced to, it used faster tempos. Beboppers introduced new forms of chromaticism and dissonance into jazz; the dissonant tritone (or "flatted fifth") interval became the "most important interval of bebop"[1] and players engaged in a more abstracted form of chord-based improvisation which used "passing" chords, substitute chords, and altered chords. The style of drumming shifted as well to a more elusive and explosive style, in which the ride cymbal was used to keep time, while the snare and bass drum were used for accents. This appealed to a more specialized audiences than earlier forms of jazz, with sophisticated harmonies, fast tempos and often virtuoso musicianship. Bebop musicians often used 1930s standards, especially those from Broadway musicals, as part of their repertoire.[2]
An early 1940s style known as "jumping the blues" or jump blues used small combos, uptempo music, and blues chord progressions. Jump blues drew on boogie-woogie from the 1930s. Kansas City Jazz in the 1930s as exemplified by tenor saxophonist Lester Young marked the transition from big bands to the bebop influence of the 1940s.
These divergences from the jazz mainstream of the time initially met with a divided, sometimes hostile response among fans and fellow musicians, especially established swing players, who bristled at the new harmonic sounds. To hostile critics, bebop seemed to be filled with "racing, nervous phrases".[4] Despite the initial friction, by the 1950s bebop had become an accepted part of the jazz vocabulary. The most influential bebop musicians included saxophonist Charlie Parker, pianists Bud Powell and Thelonious Monk, trumpeters Dizzy Gillespie and Clifford Brown, and drummer Max Roach.
In the late 1940s there was a revival of "Dixieland" music, harkening back to the original contrapuntal New Orleans style. This was driven in large part by record company reissues of early jazz classics by the Oliver, Morton, and Armstrong bands of the 1930s. There were two populations of musicians involved in the revival. One group consisted of players who had begun their careers playing in the traditional style, and were either returning to it, or continuing what they had been playing all along, such as Bob Crosby's Bobcats, Max Kaminsky, Eddie Condon, and Wild Bill Davison. Most of this group were originally Midwesterners, although there were a small number of New Orleans musicians involved. The second population of revivalists consisted of young musicians such as the Lu Watters band. By the late 1940s, Louis Armstrong's Allstars band became a leading ensemble. Through the 1950s and 1960s, Dixieland was one of the most commercially popular jazz styles in the US, Europe, and Japan, although critics paid little attention to it.
By the end of the 1940s, the nervous energy and tension of bebop was replaced with a tendency towards calm and smoothness, with the sounds of cool jazz, which favoured long, linear melodic lines. It emerged in New York City, as a result of the mixture of the styles of predominantly white jazz musicians and black bebop musicians, and it dominated jazz in the first half of the 1950s. The starting point were a series of singles on Capitol Records in 1949 and 1950 of a nonet led by trumpeter Miles Davis, collected and released first on a ten-inch and later a twelve-inch as the Birth of the Cool. Cool jazz recordings by Chet Baker, Dave Brubeck, Bill Evans, Gil Evans, Stan Getz and the Modern Jazz Quartet usually have a "lighter" sound which avoided the aggressive tempos and harmonic abstraction of bebop. Cool jazz later became strongly identified with the West Coast jazz scene, but also had a particular resonance in Europe, especially Scandinavia, with emergence of such major figures as baritone saxophonist Lars Gullin and pianist Bengt Hallberg. The theoretical underpinnings of cool jazz were set out by the blind Chicago pianist Lennie Tristano, and its influence stretches into such later developments as Bossa nova, modal jazz, and even free jazz. See also the list of cool jazz and West Coast musicians for further detail.
