During the 1940's there were many different styles of music evolving simultaneously. Cool jazz developed during the late 1940's at approximately the same time as bebop, and remained popular for several decades. Cool jazz was more subtle, moody, muted, and restrained than bebop, and may have been influenced by the harmonies of 20th-century art music composers like Stravinsky and Debussy.
Two of the most important contributors to the cool jazz style were trumpeter Miles Davisand pianist, bandleader, and composer-arranger Gil Evans. Other cool jazz musicians were saxophonists Gerry Mulligan and Lee Konitz, trumpeters Chet Baker and Conte Candoli, trombonists Frank Rosolino and Bob Brookmeyer, guitarists Wes Montgomery and Barney Kessel, pianists John Lewis, Dave Brubeck, and Lennie Tristano, bassist Red Mitchell, and drummers Shelley Manne and Mel Lewis.
http://www.hypermusic.ca/jazz/cool.html

cool jazz

noun

A style of jazz that emerged by the early 1950s, characterized by rhythmic and emotional restraint, extensive legato passages, and a reflective character.

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