21, is a composition for flute, oboe, trumpet, and strings by Samuel Barber, completed on September 8, 1944.
Hence the piece was composed in and named after the house "Capricorn" in Mount Kisco, acquired by Barber and Gian Carlo Menotti in 1943 and so-named for the maximum sunshine it got during the winter.
[2] The work was composed for Daniel Saidenberg but it is not certain whether or not it was also under the aegis of the Office of War Information—the Army unit to which Barber was assigned.
The piece is a departure from Barber's previous language, being neither atonal nor polytonal, but written in a contemporary tonal style.
Rhythmically nervous with frequent shifts of tempi, it may be characterized as neo-classical and was strongly influenced by Stravinsky.