I have designed sound for several shows at Moonlight Amphitheater. The Sound of Music is one of my favorites.
The equipment rig for Moonlight's outdoor summer season is the largest PA that I have worked with. The sound is mixed to several different zones for front of house, on stage monitors, and backstage feeds on two analog consoles with a total of 84 channels. My shows there typically involve 18-24 wireless microphones for performers and an additional 20 or so microphones in the pit for the musicians. This is all handled by a crew of four people: FOH engineer, orchestra engineer, playback tech, and wireless tech.
Although playback isn't usually a big part of musicals, this production did have an interesting cue that I would like to share. Toward the end of the story the VonTrapps sing in a local festival under the watchful eye of the Nazis. When they are discovered missing, the frenzied search is illustrated by this sound cue (and a little mayhem on stage.) The multiple elements of this sequence are routed to different speakers in front of and behind the audience. The version posted here is normal stereo.