Bop was regarded by many people as a revolution against the values of the previous [Jazz] era. At first hearing, it sounded very difficult and complicated. Parker and Dizzy Gillespie, the trumpet player, seemed to be playing many notes very fast, and the drummer and pianist accompanying them were no longer content with providing a steady, regular beat. Because of the speed of execution, the old tonal values were sacrificed (it was no longer possible to play with the former expressive vibrato), and the new music had a shrill, cooler sound. Soon it was fashionable to play "cool" rather than "hot." << less