Antiphon

An antiphon (Greek ἀντίφωνον, ἀντί "opposite" and φωνή "voice") in Christian music and ritual is a responsory by a choir or congregation, usually in the form of a Gregorian chant, to a psalm or other text in a religious service or musical work.

Antiphony is now generally used for any call and response style of singing, such as the kirtan and the sea shanty. Antiphonal music is music that is performed by two semi-independent choirs in interaction, often singing alternate musical phrases. Antiphonal psalmody is the singing or musical playing of psalms by alternating groups of performers. An antiphony is also a choir-book containing antiphons.