(συμφωνία ) originally signified the union of several voices in a chant, but by modern musicians it is applied to an instrumental composition, generally used as a kind of introductory movement to anthems and other pieces. Symphonies are introduced with good effect in the interval of the voices, and are called preludes when played before the psalmody, interludes when they mark the distinction of verses, and postludes when introduced at the close of the psalm.