Antiphonal
In alternation between two sound groups.
What it means
Antiphonal means: in alternation between two groups. Two choirs, two half-choirs, or a precentor and congregation sing alternately, section by section, and join their parts into a whole. The practice comes from the liturgy, where psalms have been sung alternately since ancient times. To be distinguished from it is responsorial singing, in which a soloist performs and the congregation answers with an unchanging refrain.
Musical use
Out of the liturgical alternating chant a compositional technique developed: composers write for two or more groups that toss to each other, overlap and finally unite. The Venetian polychoral style around 1600 in particular makes of this a space-related principle, in which the groups stand at different places in the church and the sound travels between them. Later too the procedure stays alive, for instance in orchestral works in which instrument groups are placed spatially apart. The effect rests on the fact that the ear perceives the direction and the music thereby gains a spatial dimension.
Performance practice
Before the rehearsal clarify the placement, for it decides the effect and the difficulties: the further the groups stand apart, the greater the travel time of the sound, and the more one must play by sight and not by ear. Agree on a common direction and clear signs for the transitions. Practise the seams separately, because there the danger of falling apart is greatest. Watch for the same tone colour and loudness in both groups, so that the alternation is perceived as motion and not as a break.
Check also whether the division of the groups is fixed in the notation or determined by you; in the second case it is worth choosing the distribution by tone colour and strength and not by seating order. Keep tempo and tone production uniform across the alternation, so that the groups appear as parts of a whole. Where the audience sits between the groups, the perception changes considerably — rehearse therefore as far as possible in the actual placement and hear the transition once from the hall.