Although Big Bands - meaning a jazz group that features over 10 musicians - have played a variety of different styles in jazz history, from bop to free jazz, it usually is understood to refer to the '30s and '40s, the classic era of swing. During that time, most of the jazz groups were Big Bands and they played a robust, invigorating style of swing that derived from New Orleans jazz. Swing was dance music, yet it offered individual musicians a chance to improvise musically fresh, technically complex solos. Since swinging Big Bands led by Duke Ellington, Count Basie, Benny Goodman and Tommy Dorsey were extraordinarily popular, the terms became interchangeable in the public eye. It may be disingenuous to call all Big Bands "swing" - just like all "swing" isn't performed by Big Bands - but the two are forever tied together, since they matured simultaneously. Furthermore, Big Bands from different genres, whether it's cool jazz or jazz-rock, often borrow from the Swing Big Band tradition.

(All Music Guide)