Boogie-woogie
 
Boogie-woogie was another jazz form that became popular during the 1930's. Chiefly a piano style, it used eight beats to the bar instead of four. Boogie-woogie featured the traditional blues pattern for most themes. The music had an intense quality that created excitement through the repetition of a single phrase. Albert Ammons, Pete Johnson, Meade Lux Lewis, and Pinetop Smith were among its most important artists.
 
Jazz vocalists came into prominence during the swing era, many singing with big bands. Many fine jazz singers emphasized popular songs. These singers included Mildred Bailey, Ella Fitzgerald, Billie Holiday, Nat "King" Cole, Carmen McRae, and Sarah Vaughan. Blues singing at its best can be heard in recordings by Jimmy Rushing, Jack Teagarden, Joe Turner, and Dinah Washington. In addition to singing, Nat "King" Cole was a superb jazz pianist and Jack Teagarden was a great jazz trombonist. See also Special Reports: Ella Fitzgerald: First Lady of Song.
 
Bebop
 
In the early 1940's, a group of young musicians began experimenting with more complicated chord patterns and melodic ideas in a combo setting. The group included trumpeter Dizzy Gillespie, alto saxophonist Charlie Parker, pianists Bud Powell and Thelonious Monk, and drummers Kenny Clarke and Max Roach. The style they developed became known as bebop or bop.
 
Most bop musicians had an exceptional technique. They played long, dazzling phrases with many notes, difficult intervals, unexpected breaks, and unusual turns in melodic direction. On slower tunes, they displayed a keen ear for subtle changes of harmony. Only extremely skilled musicians were able to play bebop well, and only sophisticated listeners at first appreciated it.
 
In bebop performances, musicians usually played an intricate melody, followed with long periods of solo improvisation, and restated the theme at the end. The bassist presented the basic beat for the group by plucking a steady, moving bass line. The drummer elaborated the beat with sticks or brushes on cymbals, snare drum, and tom-tom. The bass drum was reserved for unexpected accents called "bombs." The pianist inserted complex chords at irregular intervals to suggest, rather than state, the complete harmonies of the piece.
 
Hard bop
 
Bebop was followed in the 1950's by hard bop, or funk, jazz. This form emphasized some of the traditional values of jazz derived from gospel and blues music, including rhythmic drive, uninhibited tone and volume, and freedom from restricting arrangements. The hard bop leaders were drummer Art Blakey and pianist Horace Silver. Blakey led a combo called the Jazz Messengers from the mid-1950's until his death in 1990. The Jazz Messengers served as a training ground for many of the greatest soloists in jazz history. Trumpeter Clifford Brown and drummer Max Roach were co-leaders of another outstanding hard bop combo.
 
Cool jazz
 
Cool jazz originated in the works of such musicians as tenor saxophonist Lester Young, who starred with Count Basie, and guitarist Charlie Christian, who played with Benny Goodman. In the late 1930's and early 1940's, these musicians made changes in the sound and style of jazz improvisation. For example, they softened the tones of their instruments, used syncopation more subtly, and played with a more even beat.
 
In 1948, tenor saxophonist Stan Getz recorded a slow, romantic solo of Ralph Burns's composition "Early Autumn" with the Woody Herman band. This work profoundly influenced many younger musicians. In 1949 and 1950, a group of young musicians that included trumpeter Miles Davis, alto saxophonist Lee Konitz, baritone saxophonist Gerry Mulligan, and arranger Gil Evans recorded several new compositions. These recordings emphasized a lagging beat, soft instrumental sounds, and unusual orchestrations that included the first successful use of the French horn and the tuba in modern jazz. The recordings, with Davis as leader, were later released as Birth of the Cool.
 
During the 1950's, many combos became identified with the cool movement. Some of the most successful combos were the Gerry Mulligan Quartet, the Modern Jazz Quartet, and the Dave Brubeck Quartet.