Thanks for the great replies.
My goal is to use the audiwave in FCP X bc it’s just much easier. A challenge is that musicians often play with headphones, so the camera would only hear the new instrument while the musician hears the evolving master through the head phones–unless the master audio is also playing out loud. If not, it would make it tough to do audiowave sync in FCPX, I think, because the clip of, say, the sax would try to sync with the master, which at that point would also have all the instruments that came before the sax. I’m guessing FCPX would get confused at that point. However, if headphones aren’t used, or the master audio can also play out loud while each new instrument is being recorded, then each video clip will have the full master audio as well, which should make syncing easier. I’m thinking of this sequence:
1) Shoot the first instrument all the way through, video with on-camera audio (shooting with Panasonic HPX 170) and separate high quality (master) audio.
2) Shoot 2nd instrument playing to master audio, starting a few measures later, and also recording on master audio.
3) Shoot 3rd instrument playing to master audio, starting a few measures later, and also recording on master audio.
4) Etc…
I agree with Bill, this may not necessitate a multicam approach, but rather a series of stacked video segments all synced to the same master audio. I could either manually resize each to fit the screen with the other clips, or use a program like Tokyo Split (thanks for the suggestion–looks like a great plug-in). FCP should be able to sync up at the video of least the start of each new instrument segment to the master audio.
Again, thanks for the quick and thoughtful replies. Will let you know how it goes.