Todd had a lot of useful things to say on that. His most important one may be the audio comment. It’s trivial to add a digital audio recorder to your arsenal, and I’d suggest you get two: one to record a mix out of your mixer, the other, somewhere on the stage, I’d suggest clamped to the lead singer’s mic stand. This gets you a “dry” board mix and a “wet” or “live” sound, that includes the drummer and crowd/ acoustics, and you can balance these in post to keep the energy of the live venue, but with the clarity of the board mix. Sounds like it’s supposed to, or at least, like how you rehearsed it:-)
The next thing I’d suggest is, if you’re not using an app like Filmic Pro to control the phone’s camera, you need to.
And yes, either get a gimbal for the phone cam, or, something I’ve done is put an adapter on a heavy floor mic stand (no boom) to hold the cameraphone or gopro, instead of a mic; this is like a portable monopod that can stand free, yet move quickly, and if you walk with it, the pendulum effect of the heavy base keeps it remarkably stable… Its nice in that it is fast and easy to move and position and takes up nearly zero floor space.
When I need a gopro type camera to run a long time, over 2 hours, I mount it high up on a light stand and I put in the biggest memory card I can find, and add one of those ridiculously long phone charge cords they sell at gas stations, connected to a USB power cube with extension cord, or if cords would be a problem, to an external battery pack, Start it and forget it.
Regarding your gopros, (or gopro knock-offs, which I love); more of these is always better – you can get a 4K version of these in the 60-dollar price range, and it’s handy because you can punch-in to the wide shot to make fake zooms, pans, and close-ups that seamlessly match, when your final output is only 720 HD. I use this technique on practically all my band shoots because I don’t have trustworthy live bodies to operate my cameras when we’re performing and I’m on stage. My budget doesn’t allow for HeroBlack models, but I love my 60-dollar-ish 4K from iconntechs https://www.amazon.com/dp/B01H2TPL32/ref=sspa_dk_detail_0?psc=1&pd_rd_i=B01H2TPL32. People also seem to like the Yi brand.
More on the go-pros: perhaps invest in a scissor clip mount, normally used for hanging video lights from the tracks of dropped ceilings – and adapt it to mount a go pro to that for a high, unobstructed angle from head-on or 45 degrees off to left and/or right: this becomes a stable, safe wide shot/ cutaway, and shows people dancing in front of the stage. Or try a clamp to add the GoPro to a light bar or other lighting fixture. Again, it’s out of the way, but offers a fun angle. A gopro on a short mic stand off the drummer’s shoulder or next to his ride cymbal is a nice cut-away – drummers don’t always get enough camera love, but cutting to their visual moves always looks good in an edit. In high-noise environments, like close to a drummer, their mics can be a little overwhelmed, so I run a layer of tape over the mic hole as an attenuator.
I have very good luck at my usual venue with some hard-to-source ball cap/strap clamp skeleton frames for my GoPros (came with the Iconntechs cameras, wish I could find more) that let me clamp them unobtrusively to the edges of the lamp shades in our pizza joint. These give almost drone-like coverage. I’ll try to put up a pic of that mount later. My GoPros never go into waterproof cases, only these open-air “skeletons”, which also have standard photo screw threads top and bottom for tripod attachment. In high-noise environments, their mics can be a little overwhelmed, so I run a layer of tape over the mic hole as an attenuator.
A strong magnet and a flexible mount may also work in some venues to go on a door sill or support beam. Such things are cheap to put together but give awesome angles.
Finally, I have a little constructive criticism on the way the vids are cut. I know up-front that your choices of shots up to now are limited by what’s available. But going forward, with more possible angles, I’d want to see a bit more conventional cutting between a wide establisher, some close-ups, and some matching action, as well as cut-aways in appropriate places. If you get the gimbal stabilizer, a slow walk across the room from left to right and back, pointed at the center stage, would make a nice master or cut-away. You can’t deny the energy of a single shot of a great performance from close-in, but for me, cutting adds some “punctuation” to the verses and chorus that enhance the experience and keep the eye interested as well as the ear.
One Idea I have for you, is to ask a bunch of friends and family to come to a gig, and have *all* of them use they phones or camcorders at the same time, from every possible position, then multicam-cut them in post for a creative look.