As all the musicians appear to be tri-dactylids, with the crested individuals opting for fretless instruments, I suspect the penguoid is playing an EC.
I find it helpful to slow a fast tune way down to the point of accuracy. Play a jig as a waltz. Curiously, this works the other way 'round, a waltz as a jig. It seems to dislodge one's playing from the brains executive function...😊
Well, it's a wish list but thinking it through, I don't see how a master button would work other than on a melody. However, if each button ( landing pad ) had multiple functions, like a little joystick. an 88 keyboard could be reduced to 52........😊
Playing for that long at a stretch, especially as a beginner, is counterproductive at least for me. Unless you're a cyborg your brain will be overwhelmed and stop processing after about 20 min. or so. Roughly 20 min. every other day is optimum for my particular lump of grey matter. With your sore arm I'd stop as soon as it starts to hurt. Combine that with Alan's suggestion to play quietly to give both your brain and body a chance to recover.