I literally just improvised XD Sorry it's kinda awful :3 I'm like "Yeah I'll hit a high Bb that's way higher than any sane tuba player in seventh grade should hit! Why not? :D" Mostly in Bb major, but I threw a couple accidentals to keep things interesting. I promise, i actually changed dynamics XD This is just without my good mic so you can't really tell, sadly.
It's a loop, beware.
