Editing the material is going to be a major challenge. I don't know whether you will get help from more knowledgeable people than me, but this roughly how I would do it. I suppose that the audio performance was recorded using a multi-track system.
- first, I would decide what will be going my "main camera" for the major takes and note the position of the actors on screen on these takes
- then, I would mix the audio so that the actors position on that camera is consistent with the mix
- then, I would color correct the footage from all cameras so that they look similar (it is a standard function on most editors). I would also de-noise and correct contrast at that point. You may want to crush the blacks a bit to hide the cameras' noise.
- then I would edit the 3 performances separately (on that part, see below)
- finaly, I would cut from the 3 edited performances
For the actual editing, depending on your editor and computer, you have two choices: you can synchronize all takes to the soundtrack and edit in multicamera mode. This is easier, but you'll need a very powerful computer and hard disks for 5 cameras in HD. You'll also need to choose the right codec: too compressed and your processor won't be able to decompress 5 streams in parallel, easier to decode and the 5 files will be too big to stream from your hard disks. The other choice is to keep the files unsynchronized, but it is much more work.
A caveat: don't forget to mix your audio to 48 KHz. Software makes it appear that other frequencies should work, but they never stay synchronized.
All these being said, I would not edit the full show, but make a digest of it, keeping the best arias for example. This should be far enough work already and my experience has shown that the artists prefer a digest, because the main use for them will be a promo DVD.
