A sextet (or hexad) is a formation containing exactly six members. It is commonly associated with vocal ensembles (e.g. The King's Singers, Affabre Concinui) or musical instrument groups, but can be applied to any situation where six similar or related objects are considered a single unit. Many musical compositions are named for the number of musicians for which they are written. If a piece is written for six performers, it may be called a "sextet". Steve Reich's "Sextet" is written for six percussionists.