From The Art and Popular Culture Encyclopedia
A musical ensemble is a group of two or more musicians who perform instrumental or vocal music. In each musical style or genre, different norms have developed for the sizes and composition of different ensembles, and for the repertoire of songs or musical works that these ensembles perform.
In classical music, trios or quartets either blend the sounds of instrument families (e.g., piano, strings, and winds) or group together instruments from the same instrument family, such as string ensembles or wind ensembles. In jazz ensembles, the instruments typically include wind instruments (one or more saxophones, trumpets, etc.) one or two chordal "comping" instruments (electric guitar, piano, or organ), a bass instrument (electric bass guitar or double bass), and a drummer or percussionist. In rock ensembles, there are usually several guitars (one or two electric guitars, a bass guitar, and in some cases, one or more acoustic guitars), a keyboard player (either a Hammond organ, a piano, an electric piano, or an electronic synthesizer), and a drummer.