I've finally done it! I've recorded a full video of all 8 drives playing a full song!
It's not that it wasn't capable of finishing a song, it's just that my spare time had disappeared and recording-specific things were not ready. Also, the generated visualisation needed to be updated.
Luckily, thanks to the power of Object Oriented Programming and me leaving the note status methods intact, porting the visualiser to the overhauled instrument system didn't take too long. Most of the time was spent arranging the LEDs in the corner. I had an implementation where the LEDs were generated from the instrument controller list, and while this did work, I decided to instead hardcode the LEDs to match the physical location of the instruments.
I'm thinking of swapping the Fubarino for an Arduino Mega I'm not using (I need the Fubarino's extra RAM and small size in a robot project), but I've decided to stop myself for now, or otherwise it would've taken me even longer to make a video of the Orchestrahestra. It will probably be happening in the near future.