Ok, this is a post I've long considered where to put... there is so much in it (yet not in depth). Let it rest here, and see what comes of it.
Yesterday, we played a concert, "Musc from Animated Movies". Choir, kids, choir, small smphonic orchestra, combo. Titles ranged from "When you wish upon a star" to "Happy", with excursions into Shrek, Hunchback of Notre Dame, Jungle Book and the like. Venue, a large, somewhat unorthodox school hall: One central hall three storeys high, with two large open staircases doubling as seating leading down, and an additional wing with seating. Seating all over, up to the top (with the audience being on two balconies, as it were).
One staircase had to be kept free as eergency exit, so we placed the stage there. Front to back: Kids, Choir, Combo, Orchestra (with the orchestra well hidden from the audience's view by the choir). Conductor directly in front of the orchestra, conducting the choir via a camera and screen arrangement.
At rehearsal, everyone complaining that they could not hear a thing. Sound going off into Nirvana, so bad you could barely hear yourself.
Performance: Hall filled with 800+ audience (oversold, and some people standing around in the aisles contrary to fire prevention regulations...
And the hall suddenly came alive! One really could hear the whole structure... wonderful. I had a one-brand gig bag with me - Courtois flugel, Courtois C, Courtois Balanced Bb. And that old Balanced Courtois made the day - filling the entire hall without amplification.
Correction: I had the ACB picc with me as well, for "Fairytale" from Shrek, but that was in it's own case... read more there.