1940s in jazz 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". 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. The swing era lasted until the mid-1940s, and produced popular tunes such as Duke Ellington's "Cotton Tail" (1940) and
The Genius of Charlie Parker Vol. 2" [Savoy MG 12009] and "The Charlie Parker Story" [Savoy MG 12079]) completing the reissue of the previously released master takes, and the original issue of most of the unreleased takes from these seven sessions. Parker's entire Savoy ouvre was finally issued on "Charlie Parker: The Complete Savoy Studio Sessions" in 1978. The master take of "Koko", included here, is controversial in that it is unclear who, precisely, plays trumpet and\or piano on the track. The liner notes credit Miles Davis with trumpet for the session, but also credit Dizzy Gillespie with both trumpet and piano. Several sources claim