In the early 1940s in jazz, bebop emerged, led by Charlie Parker, Dizzy Gillespie, Thelonious Monk and others. It 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" 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