By the end of the 1940s, the frightened energy and strain of bebop got replaced with a bent towards calm and smoothness, with the sounds of cool jazz, which favoured long, linear melodic lines. It appeared in NY Town , due to the mix of the styles of mainly white jazz musicians and black bebop musicians, and it controlled jazz in the first part of the 1950s. The kick off point were a collection of singles on Capitol Records in 1949 and 1950 of a nonet controlled by trumpeter Miles Davis, picked up and released first on a ten-inch and later a twelve-inch as the arrival of the Cool.

Cool jazz recordings by Chet Baker, Dave Brubeck, Bill Evans, Gil Evans, Stan Getz and the Modern Jazz Quartet generally have a "lighter" sound which evaded the assertive tempos and harmonic condensation of bebop. Cool jazz later was strongly identified with the West Coast jazz scene, but also had a selected resonance in Europe, particularly Scandinavia, with emergence of such major figures as baritone saxophone player Lars Gullin and pianist Bengt Hallberg. The unproven under structure 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 more detail.