Cool jazz is a variant of bebop, mostly played by white people, in which the musicians tried to control their emotions a bit more. The tempo's were lower than in bebop and (just like in swing) there was more attention for arrangements and consonant sounds. The white pianist Lennie Tristano, one of the great initiators of cool jazz, didn't want rhythmic tricks from the drummer but an even pulse over which the horns played with almost surgical precision. Around 1950 trumpeter Miles Davis set the tone for a softer, more subtle way of playing with the release of Birth of the Cool, music for a 9-man formation arranged by the white arrangers Gil Evans and Gerry Mulligan. Mulligan, a renowned baritone saxophonist, along with musicians like Shorty Rogers and Art Pepper, was one of the most important exponents of West Coast jazz, a cool jazz related style that was played mainly by white musicians who worked in California's studios.