For that matter, a kit drummer is essentially playing (up to) four instruments at once since each limb could be doing something unique (granted for many (most?) drummers, they’re just using the high-hat pedal as a footrest, beating quarter or half notes on the bass drum and their hands will be focused on a single instrument, but a truly talented drummer might have four unique rhythms going at once). Add in the fact that some drummers sing backup and it can be quite impressive.

I had the pleasure of working with an amazing organist in my time at Holy Name Cathedral (he’s apparently since become semi-retired, just doing occasional fill-in work). Watching him do a Messiaen organ piece as a postlude after Mass it was like seeing video of Keith Moon on the drums. Limbs moving in a seemingly chaotic manner and yet music came out the other end (on top of crazy multi-manual keyboarding and pedalwork, he was also frequently changing the stops on the organ as he played).

Nice. Oh yeah for sure that makes sense. I also think of the locking in a limb to play a preset "pattern loop" is also really similar to juggling which is something I enjoy. Just a lot of overlap in general!