I was in a church today that considers itself to hold strictly to the regulative principle of worship (that which is not explicitly commanded for public worship in Scripture is implicitly condemned) and was puzzled that a choir sang an offertory—sang without the congregation during the taking up of the offering. I am wondering, given their position on worship, what the Biblical justification for this practice might be. Is this practice defensible from Scripture, given the regulative principle?
There are a number of times that the Psalms have a call and response to them (there is one which has "for his love endures forever" as the second half of every verse). The liturgy which is shown in the book of Revelation has a clear chorus which is separate from the congregation (elders who bow down are separate from the great multitude). If it is possible for one subset of the congregation to sing a part of a song, why would it be impossible for one subset to sing the entire song?