Many of the big bands who were deprived of experienced musicians because of the war effort began to enlist young players who were below the age for conscription, as was the case with saxophonist Stan Getz's entry in a band as a teenager. This coincided with a nationwide resurgence in the Dixieland style of pre-swing jazz; performers such as clarinetist George Lewis, cornetist Bill Davison, and trombonist Turk Murphy were hailed by conservative jazz critics as more authentic than the big bands. Elsewhere, with the limitations on recording, small groups of young musicians developed a more uptempo, improvisational style of jazz, collaborating and experimenting with new ideas for melodic development, rhythmic language, and harmonic substitution, during informal, late-night jam sessions hosted in small clubs and apartments. Key figures in this development were largely based in New York and included pianists Thelonious Monk and Bud Powell, drummers Max Roach and Kenny Clarke, saxophonist Charlie Parker, and trumpeter Dizzy Gillespie. This musical development became known as bebop. Bebop and subsequent post-war jazz developments featured a wider set of notes, played in more complex patterns and at faster tempos than previous jazz. According to Clive James, bebop was "the post-war musical development which tried to ensure that jazz would no longer be the spontaneous sound of joy ... Students of race relations in America are generally agreed that the exponents of post-war jazz were determined, with good reason, to present themselves as challenging artists rather than tame entertainers." The end of the war marked "a revival of the spirit of experimentation and musical pluralism under which it had been conceived", along with "the beginning of a decline in the popularity of jazz music in America", according to American academic Michael H. Burchett. With the rise of bebop and the end of the swing era after the war, jazz lost its cachet as pop music. Vocalists of the famous big bands moved on to being marketed and performing as solo pop singers; these included Frank Sinatra, Peggy Lee, Dick Haymes, and Doris Day. Older musicians who still performed their pre-war jazz, such as Armstrong and Ellington, were gradually viewed in the mainstream as passé. Other younger performers, such as singer Big Joe Turner and saxophonist Louis Jordan, who were discouraged by bebop's increasing complexity pursued more lucrative endeavors in rhythm and blues, jump blues, and eventually rock and roll.