It's been a bit crazy (the theater business is like that, and so is the starving artist lifestyle. The combination....!)
When I have time to post properly, I think it might entertain some to look at the microphone setups I've worked with (my designs and others) on actual stage shows. Very often, these are driven not by studio aesthetics, but by lack of equipment, lack of space for the orchestra, lack of anything resembling an A2 or other person who can be trusted to get them in the same position from night to night, and of course from lack of time.
The unfortunate reality is that when most companies produce a musical they forget that the word music is right there in the description. So there is eight thousand dollars for a rental set. Six lighting technicians working for two days to get the lights to look great. But not a dollar to replace aging microphone elements -- some shows, you can't even get fresh batteries!
And as far as the actual need goes: in many productions, the band will be too loud to begin with. You are fighting to get control of them so you can get the singers heard -- without simply putting the singer's microphones up to 11, which sounds horrible and hurts ears and is really no solution at all. Make friends with the vocal director. Get a rapport and a dialog with them. Not only do they often have more pull with the director, they are also the artist you are trying to support; the person who knows what they were trying to achieve vocally from moment to moment. Look to them for advice as well as for support.
A small but unfortunate number of conductors, on the other hand, consider their job starts and ends with the pit. A band can get insular; they have their own call time, they don't share the dressing room, they weren't involved in most of the rehearsal process. They show up on their own schedule and keep to the pit through the show. Sometimes you have to get down there and strike up conversations and act as a gentle reminder that there is a SHOW up there on the stage floor above them.
Still, the majority of conductors understand that they work within the total sound of a show, and are not just happy but eager to have trusted ears outside the pit that can tell them if the underscore is at an appropriate level.
Practically speaking, then, it is rare that the band isn't loud enough. If volume were all that there were in the world, you wouldn't need to do anything further. Here is where the hard sell begins; with judicious mic'ing, you might increase the total VOLUME slightly, but you achieve a much better placement, tone quality, and focus.
Also practically speaking, monitors can never be too loud for actors. They will always want more. More often than not you end up with stomping levels of piano -- a sound that completely distracts from the orchestral blend desired -- because the actors whine if you try to turn it down.
All of this often ends up with you cramming what microphones you can spare in what spaces you can find just to lift up the actual tone of the instruments from the wash of reflected and reverberant sound. In this, however, even a single mic gives the final orchestral sound something positive it didn't have before. So even if all you have is a single Radio Shack PZM, and the only place you can stick it is on the actual side of the pit, it may still be a net improvement to the sound of the show.
And, at that, it is a great chance to experiment; trying out different mics, different placements, messing with EQ to see what elements you can bring out.
When I come back to this, I'll have some scans of the drawings from actual productions in which we did pretty much that. Perhaps I'll remember to photograph a few set-ups next time I make them, too.