Avant-garde jazz of the 1940's, and the foundation for subsequent eras. Added a little rhythmic, harmonic, and melodic complexity to the conventions of swing-era jazz - and a lot of people didn't get it as a result. Charlie Parker, Dizzy Gillespie, Thelonious Monk, Bud Powell, Max Roach, and Kenny Clarke were some of the movers and shakers of the era, which marked the beginning of the end for jazz as a mass-market dance music. Good.