Church choirs: Cultivated excellence or "everybody welcome!"?

Holy Week and Easter are matched only by Advent and Christmas as
prime times of the Christian year for showcasing choral singing. This
has me thinking about church choirs generally–what are they for and who
should sing in them? Maybe not burning questions in light of more recent
theological controversies (is there a hell and is anybody in it?), but questions I’d like a little more clarity on. And since I blog so that I might know better what I think about this or that subject, here goes.

What are church choirs for? There’s a long history of
liturgical choral singing in Judaism and Christianity that can’t be
rehearsed here, so let me cut to the chase: Since most Protestant
churches don’t sing or chant much, if any, of the liturgy, what’s the
role of the choir in today’s worship? (And, by the way, after 20+ years
of a Psalter in the back of the hymnal, why don’t United Methodists sing
the Psalms? I don’t mean the “musical responses” but the actual Psalms
themselves. That’s what those little red dots over some of the words are
for, along with the instructions and tune (tone) options on page 737.
In worshiping in lots of UM congregations through the years–large and
small, urban and rural, high- and low-church, I’ve rarely experienced
it, though I did try to teach it once to a small group of church
leaders. They were game; the results were mixed. But I digress).

Church choirs often seem to be performers rather than, say, partners
in worship. (Modern church architecture with centrally-placed
choir ”lofts” only aids this impression). That is, from on high the
choir sings a “special” (a favorite word of many small congregations–and
maybe peculiar to the South, I don’t know), sometimes even eliciting
applause from the audience, er, congregation. The idea that the choir
might have a subtler, richer role to play doesn’t seem to have much
purchase.