Have you ever thought of dipping into the late medieval repertoire? We've tried it without much success in the past. Seems a bit too remote for parishes, and not worth in the effort, at least in what we've tried. But Michael Lawrence alerted me to a piece that is just splendid, by the English composer Lionel Power who died in 1445). It's for three parts. The piece is for Christmas: Beata proginies.
Here is the score.
And here is a midi.
Text:
Beata progenies unde Christus natus est;
quam gloriosa est virgo que caeli regem genuit.
Blessed is the parent from whom Christ was born;
O how glorious is the virgin who brought forth the King of heaven