Bebop had revolutionized Jazz and started the era of “Modern Jazz”. It had done away with the “dance craze” and light entertainment of the Swing era, which sounded always suddenly anachronistic after the World War II.
Bebop did not depend on the taste of the masses and brought back the blues into Jazz. It was played by small ensembles in small clubs; a music to listen to, as opposed to dance to.
However, in this very fundamental transition from Swing to Bebop, Jazz had lost large parts of its audience. In the 1950s jazz lost its dominant position within the recording industry, first surpassed by the pop vocalists, then by rock music, then even by soul music. The major labels looked always suddenly elsewhere to increase their profits.
Good musicians could really show all their talent in Bebop as it placed a lot of emphasis on the soloist and the improvisation. But some felt that his had gone even too far. To produce a new record, one had basically to get the house rhythm section and hire Parker, Gillespie or J.J. Johnson, which would improvise over known standards for one hour. No rehearsal required, no arrangements to be written beforehand.
But then “Birth of the Cool” was released. Although only from today’s point of view this can be seen as the defining point of Cool Jazz. “Birth of the Cool” was actually only issued under this name in 1957 and was a compilation of two recordings done by the Miles Davis Nonet in 1949 and 50.
But Cool Jazz was a reaction to the hectic, loud Bebop. It was on the one hand softer and easier to listen to as Bebop, but was actually more extreme than Bebop.
The name came from the lighter, cooler sound the players used. Lester Young was a very important influence with regards to the “Cool” sound. Young’s saxophone playing employed a light sound, in contrast to the “full-bodied” approach of players such as Coleman Hawkins. Young also had a tendency to play behind the beat, instead of driving it.
But “Cool” sound can actually traced back to the very early phases of Jazz, to players like Bix Beiderbecke and Frankie Trumbauer.
While this sounds like Cool Jazz being a rather conservative and easy-listening version of Jazz, it is anything but that. The founders of Cool Jazz grew up with Bebop and not with Swing, e.g. Miles Davis with Charlie Parker, the Modern Jazz Quartet with Dizzy Gillespie, Stan Getz with Woody Herman, Gerry Mulligan and Art Pepper with Stan Kenton, Paul Desmond with Dave Brubeck.
Cool Jazz is a cerebral kind of music. It is largely independent of the traditional preoccupation with rhythm and melody. It focuses on creative sounds in a “cool” (calm, pensive, meditative) fashion, largely dispensing with the original features of Jazz like syncopation and melody.
Additionally, some orchestras of the Cool Jazz blended Jazz and Classical Music, which eventually led into the “Third Stream” era.
Unlike bebop, much of Cool Jazz was arranged (written) ahead of time. The balance between arrangement and solo as well as soloist and orchestra was more equal than in Bebop.
Whereas Bebop bands were usually a quartet or quintet and were comprised of saxophone and/or trumpet and rhythm section, Cool Jazz groups had a wider variety of size and instrumentation.
Commonly two terms are used to name this genre, “Cool Jazz” and “West Coast Jazz”. According to my understanding, it does not add to the quality of the discussion trying to separate the two. Therefore “Cool Jazz” is used throughout this post, but it includes “West Coast Jazz”.
Cool Jazz finalised transition away from entertainment to pure musicians music. The musician metamorphosed from being an entertainer to being an explorer. Miles Davis would hardly announce songs in concerts, and certainly would not make jokes to entertain the audience.
Despite this, Cool Jazz actually re-popularised Jazz, and brought some of the audience back to Jazz. And with Cool Jazz, the music even moved to Campuses and was not only played in nightclubs.