ANTIPHON - (pl. antiphons) a general title for a hymn or a section of the Psalter; the title describes the manner in which the hymn or Psalter are to be chanted, i.e., by two choirs in turn.
An antiphon consists of one or more psalm verses (or sentences from Holy Scripture), alternating with verses which contain the fundamental thought of the psalm. The name derives from the traditional practice of their being sung by two choirs, each responding antiphonally to the other.
In modern Orthodox practice, one choir or set of chanters may sing all the parts alone, but where there are two choirs or chanters alternating such hymns, the music is said to be antiphonal. The Byzantine churches tend to perform music in an antiphonal fashion more often than the Slavic.