Swing come back in the forties even if it was declining before. This is in reaction to bop that some people found to aggressive. This type of jazz used a lot of instrumentation: Trumpet; clarinet; trombone, sax, piano; guitar (usually), bass, drums. And sometimes horns. Swing rhythm is emphasised, with drums using ride cymbal and brushes extensively. Horns use the phrasing and harmonic language of swing. The approach is either a jam session in a swing style with collective improvisation opening or closing the performance; or the horns scored in harmony in a big-band-type arrangement.
Bebop.
In the 1940's some Jazz musicians began to break away from swing music and involved a new style of Jazz known as Bebop. The Bebop era represents for many the most significant period in Jazz history. Several consider it the time when musicians began to put innovation ahead of convention and looked towards the future instead of paying homage to the past. Charlie Parker, an alto saxophonist, was a key figure in the development of Bebop along with Louis Armstrong and trumpeter Dizzy Gilles pie. Bebop was a Jazz style that stressed melodic improvisation and flourished between 1944 and 1958. Jazz changed forever during the Bebop years.
Instruments used.
There are no musical instruments that a truly unseen in jazz - virtually every one has been used by jazz musicians at one time or another, including all of the instruments of the European classical ensembles. Some instruments, once in favor, have gone out of style - the banjo for example, largely replaced by the guitar in the 1930's, where a smoother, quieter form of rhythm and chords was required. Other instruments have virtually disappeared only to come back later with a different role to play. This is seen with the tuba, which began as a rhythm instrument, and was replaced by the stringed bass at the end of the 1920s but returned in the late 1940's. Others, like the clarinet, once one of the most popular of instruments, faded, and have never made a complete return.