Revolt against bop, more relaxed and understated. Three main characteristics: unique sonority, delicate attacks, little or no vibrato, played in the middle range of the instrument. Phrasing: not regular length, not limited to 12 or 16 bars. Overlapping phrases, one player begins a solo before the other is finished. Orchestral concept: ensemble of 3 to 8 players, using instruments new to jazz, French horn, flute, cello, vibraphone etc. Unusual metres common, (3/4, 5/4, 9/4, 19/4). classical form sometimes used. Rondo, fugue,etc. Famous, Miles Davis, Dave Brubeck.