I've never called a mic cue on a musical. I've also never worked with a sound operator who is on comms during the show; they always have comms, in case something goes wrong, but apart from coming on at the top of each half to tell me that all is well (or we need to hold while he checks that someone's mic is OK), they're never on comms during the show, because as someone said, you can't hear the show properly when you've got one ear covered. Usually I keep out of mic plot discussions - I tend to leave that one to the sound operator/designer and the MD. If you haven't got enough mics for everyone who has lines to have one, then no, don't mic the dialogue as it will sound very uneven. My current sound operator got sent an electronic version of the script and a cast list about four weeks out from tech week; he came to a run, asked me a few questions (mostly about lines which have been slightly redistributed as we cut some minor characters), had a chat with the MD and turned up at tech ready to go. He operated from script for the first little while, and has gradually made himself up cut versions over the run, until now, 11 weeks in (one week to go! woohoo!) has his script down to half a page - reminders for particularly tricky cues which have caught him out. He certainly doesn't get cues to turn people's mics on and off; the cast know to keep quiet for the first 30 seconds that they're offstage after a scene but other than that, he's totally on his own. To complicate matters, any cast members who are offstage in numbers are singing as well, so there are quite a few cues which are not in the script, as that particular person is not in the scene and so not mentioned. Basically, I just leave him to it and he does a great job!