Duet
A duet is a musical composition for two performers in which the performers have equal importance to the piece. It is often used to describe a composition involving two singers. It differs from a harmony, as the performers take turns performing a solo section rather than performing simultaneously. In classical music, the term is most often used for a composition for two singers or pianists. A piece performed by two pianists performing together on the same piano is referred to as "piano duet" or "piano four hands". A piece for two pianists performing together on separate pianos is referred to as a "piano duo".