A septet is a formation containing exactly seven members. It is commonly associated with musical groups but can be applied to any situation where seven similar or related objects are considered a single unit, such as a seven-line stanza of poetry.
The modern composerBohuslav Martinů wrote three septets: a group of six dances called Les Rondes for oboe, clarinet, bassoon, trumpet, two violins, and piano (1930); a piece called Serenade No. 3 for oboe, clarinet, four violins, and cello (1932); and Fantasie for theremin, oboe, piano, and string quartet (1944). Darius Milhaud composed a string septet in 1964 for string sextet and double bass. Paul Hindemith composed a wind septet in 1948 for flute, oboe, clarinet, bass clarinet, bassoon, horn, and trumpet. Hanns Eisler composed two septets, both scored for flute, clarinet, bassoon, and string quartet: Septet No. 1 Op. 92a ("Variations on American Children's Songs") (1941), and Septet No. 2 ("Circus") (1947), after Chaplin’s 1928 movie The Circus. Two component works in the series of Chôros by the Brazilian composer Heitor Villa-Lobos are scored for seven instruments: No. 3 (1925), subtitled "Pica-páo" (Woodpecker), is for clarinet, bassoon, saxophone, 3 horns, and trombone (or for male chorus, or for both together), and No. 7 (1924), actually subtitled "Septet", is for flute, oboe, clarinet, saxophone, bassoon, violin, and cello (with tam-tam ad lib.).
Kube, Michael. 2001. "Septet". The New Grove Dictionary of Music and Musicians, second edition, edited by Stanley Sadie and John Tyrrell. London: Macmillan Publishers.