These are the very first things that came to mind. We don't know enough about the type of performance nor the venue to be able to give proper advice. From what I've been reading this sounds like a concert. Is this correct? If so, what kind? Rock band? Jazz Band? Orchestra? I also saw the phrase "musical" thrown in there, and that's a completely different beast.
I've done stuff like this before, but in order to help I'd need to know exactly what type of performance this is, as well as what is being used for live sound reinforcement. Is there a FOH mixer? What kind? How many channels of audio are they mixing (number of mics)? Can you take a board feed? Are they running technical rehearsals ahead of time or a sound check?
When I've done live orchestral recording I do an X/Y setup on a stand above the orchestra right behind the conductor and run that to my mixer, and then recorder. 2 tracks usually just fine for this. For a live band I'd take a feed from the FOH mixer. This feed is usually sent on an aux send from the board that is a line level out 2 channel mix. The FOH board will dictate and the person operating it will dictate how this comes to you. If it's aux sends you need to be careful because many live mixers have a separate mix for the aux sends than they do for the main mix to the house mains. Some mixers have a separate stereo send. For example, I've run boards that have XLR or quarter inch outputs for the main L/R audio sends to the main speakers, and then there will be another set of outputs with the same signal on something like quarter inch or eighth inch, or RCA, or some other connector. So, in order to be able to have the proper cables you need to know what the board does.
As you can see, there are lots of variables, which is why communication with the FOH mixer before hand is really important. You need to communicate what you are doing and what they are willing to send you. Some FOH mixers don't want to be bothered with doing a separate mix for aux sends because that's another thing they have to deal with on top of everything else they are doing. Some don't mind.
You can take the outputs of the FOH mixer and run those into a wireless transmitter and send that to receivers on the camera. I honestly prefer to do that hardwired, though.
To be honest with you, if it were me doing this, I'd have an audio feed that goes to camera, and that'd be just a scratch track, and I'd record the audio on a separate audio recorder, but that requires more equipment and the know-how to use it all and manage it all.
