Two bodies, two primes, no bag. Why the zoom stays in the car.
Three songs is not a lot of time, and a pit is not a lot of room. Every extra piece of gear is something to trip over, something to swap, something between you and the frame. So the kit gets cut down to what earns its place: two camera bodies, a wide prime on one and a short telephoto prime on the other.
The zoom stays in the car because it makes me lazy. With primes, I move my feet, and moving my feet is where the better frames come from. No bag means no fumbling, and no fumbling means I am watching the stage instead of my hands.
That is the whole system. It is not clever, but it holds up when the lights do something unexpected, which they always do.