They said $1000-$1500 and I think a used GH4, 35-100 f2.8 and shotgun mic should be doable for about that money...
If I was shooting live music with a $1,000-$1500 budget, I'd get the GX85 with the two lenses for under $600, and a G7 with the 14/42 lens for under $500, and use the iPhone (possibly with a telephoto clip-on lens) for the third, roving camera. If the OP wants to use a mic attached to the camera, I'd use the G7 body for that, since it has a mic input.
I'd put the 45/150 lens on the lead singer for a portrait view, and the other camera on the wide shot, using the 14/42 if the 12/32 isn't long enough. With this basic three-camera setup, the OP would only have to keep track of the 30 minute time limit on the G7 and restart it accordingly. (The shooter would probably have to stop and restart the iPhone to get around the time limit, but as long as the beginning of the new song is captured, it's not hard to sync up the video in the editor.)
The drawback to the G7 (besides the 30 minute time limit for video) is the fact that it does not have in body image stabilization like GX85 or G85 has. Panny mitigates this shortcoming by offering optical image stabilization on some of its lenses. For tripod-mounted cameras, IBIS and/or OIS are supposed to be turned off, so in this one shooting scenario, image stabilization would be irrelevant.
The OP would still have money left over for a Zoom to record good audio.
I hope we're being helpful...
More information helps lead to better decisions. For this one particular shooting scenario, this would be how to get the best bang for buck and most interesting end product. Spending the entire budget on one camera might pay off in the long run if the OP plans on expanding to other avenues of video, but for this one particular shooting scenario, it would be throwing away half the budget.
The other issue of buying into the Panasonic line is autofocus. It's pretty much useless for video. In this one shooting scenario - cameras on tripods shooting subjects that stay in place - you don't need AF, but if one expands into other avenues of video, a more expensive Sony camera could be a better choice because the autofocus is more reliable. Even then, one would need to research which Sony cameras have good AF for video and don't overheat.
The issue of batteries is easily solved via the $18 AC adapter route, or if the OP doesn't need to shoot more than 90 minutes at a time, the stock batteries fall within that range. Or, one can pick up an external usb battery pack to use in conjunction with a DC coupler (fake battery) to extend shooting times. If I'm expecting to be shooting for longer than 90 minutes, I mount the external battery to the tripod via a velcro strip. They're good for 6 to 8 hours or more and generally cost less than another factory battery for the camera.
If the OP does go the multi-camera route, a good approach would be to transfer the wide view camera to DVD (or Youtube as an unlisted link) and let the subject choose a song or two for the multi-camera edit. Doing a multi-camera edit of an entire one hour show could be a very time consuming process.
When dealing with young performers, these videos could be priceless in the sense that they're capturing a moment in time that will never be repeated. In that sense, going all out with a 3-camera shoot could really add value to the process - not necessarily monetary value, but value to both the musicians and the videographer. And, if a parent wants a multi-camera edit, it wouldn't be unreasonable for the videographer to let them know how much time it would take, with a modest price attached to that time. Parents love spending money on their kids.
(Considering that, with this budget, there would still be money left over, I'd add a $200 Yi camera behind the drummer. You can thank me later.

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