Alternatively, the accompaniment to a vocal melody or instrumental solo can be provided by a musical ensemble, ranging in size from a duo (e.g., cello and piano; guitar and double bass; synthesizer and percussion); a trio (e.g., a rock power trio of electric guitar, electric bass and drum kit; an organ trio); a quartet (e.g., a string quartet in Classical music can accompany a solo singer; a rock band or rhythm section in rock and pop; a jazz quartet in jazz); all the way to larger ensembles, such as concert bands, Big Bands (in jazz), pit orchestras in musical theatre; and orchestras, which, in addition to playing symphonies, can also provide accompaniment to a concerto solo instrumentalist or to solo singers in opera. With choral music, the accompaniment to a vocal solo can be provided by other singers in the choir, who sing harmony parts or countermelodies.