I know some don't have time or believe in doing warm-ups, but it's a necessity for my schola who is mostly made of singers who have minimum experience with singing in choirs, come to rehearsals and cannot gear to 'singing voice' without some sort of transitional tools. Also we are keep working on deep-breathing and diction etc. for a resonant sound and blending. (15 minutes max. though, so not to overburden them)

Do you have any choral warm-up books that you like?

Recently, I've been re-reading James Jordan's, 'Evoking Sound, The Choral Warm-up,' which has lots of good info,. and vocal exercises with physical gestures.

The following is a beautiful paragraph from his book that I want to remember when I do warm-ups,

'...Awe and wonder are the only true vehicles for music making. Great music, by its very composition, is infused with awe and wonder. But its sonic beauty will never be realized unless the choir sings through the door of awe and wonder. Arrival into and at the state of aesthetic fantasy, and ultimately a heightened state of aesthetic reality, should be one of the over-riding and compelling objectives of any warm-ups or rehearsal. Sound is the by product of awe and wonder."