A corollary to the fact that the congregation is the primary musical group in the church, is that the primary function of the choir is to help the congregation sing better. The choir is not to be a performing group where the musical elite of the church prepare and present aesthetic delights to the wonder of the rank and file. Rather they are to use their gifts to undergird, support, enhance, strengthen and embellish the corporate ministry of song.

The most obvious contribution that a choir can make is that of sonic support for the people’s song: in terms of volume (especially in a room which is on the dead side acoustically), depth (strengthening the bass), fullness (adding harmony by singing in parts), and tempo (helping to set and maintain it). In addition, the presence of a choir singing in parts makes possible effective a cappella singing at climactic or reflective moments.

from “The Choir as Worship Leader: Revitalizing the Ministry from the Loft”