A big band is a type of musical ensemble associated with playing jazz music and which became popular during the Swing Era from the early 1930s until the late 1940s. A big band typically consists of approximately 12 to 25 musicians and contains saxophones, trumpets, trombones, and a rhythm section. The terms jazz band, jazz ensemble, stage band, jazz orchestra, and dance band are also used to refer to this type of ensemble. This does not, however, mean that each one of these names is technically correct for naming a 'big band" specifically.
There are two distinct periods in the history of popular bands. Beginning in the mid-1920s, big bands, then typically consisting of 10–25 pieces, came to dominate popular music. At that time they usually played a sweet form of jazz that involved very little improvisation, which included a string section with violins, which was dropped after the introduction of swing in 1935. The dance form of jazz was characterized by a sweet and romantic melody. Orchestras tended to stick to the melody as it was written and vocals would be sung sweetly (often in a tenor voice) and in tune with the melody. .