In the early 1940s bebop performers helped to shift jazz from danceable popular music towards a more challenging "musician's music." Differing greatly from swing, early bebop divorced itself from dance music, establishing itself more as an art form but lessening its potential popular and commercial value. Since bebop was meant to be listened to, not danced to, it used faster tempos. Beboppers introduced new forms of chromaticism and dissonance into jazz; the dissonant tritone (or "flatted fifth") interval became the "most important interval of bebop"[48] and players engaged in a more abstracted form of chord-based improvisation which used "passing" chords, substitute chords, and altered chords. The style of drumming shifted as well to a more elusive and explosive style, in which the ride cymbal was used to keep time, while the snare and bass drum were used for accents. These divergences from the jazz mainstream of the time initially met with a divided, sometimes hostile response among fans and fellow musicians, especially established swing players, who bristled at the new harmonic sounds. To hostile critics, bebop seemed to be filled with "racing, nervous phrases".[49] Despite the initial friction, by the 1950s bebop had become an accepted part of the jazz vocabulary. The most influential bebop musicians included saxophonist Charlie Parker, pianists Bud Powell and Thelonious Monk, trumpeters Dizzy Gillespie and Clifford Brown, and drummer Max Roach.