Oxford English Dictionary. Antiphon. [Etymology: Greek "in return" + "sounding"]
1. A versicle or sentence sung by one choir in response to another.
2. A composition, in prose or verse, consisting of verses or passages sung alternately by two choirs in worship . . . .
4. transf. A response, answer.
Antiphony. 1. Opposition of sound; or harmony thereby produced.
2. A musical response; a responsive musical utterance, the answer made by one voice or choir to another.
3. Alternate singing or chanting by a choir divided into two parts; antiphonal singing.
Wikipedia: Antiphony is now generally used for any call-and-response style of singing . . . . Antiphonal music is music that is performed by two semi-independent choirs in interaction, often singing alternate musical phrases
Antiphonal. A. adjective 1. Of the nature of an antiphon; sung alternately.
2. Responsive in sound, or (transf.) other effect.