I think everyone uses decimal (base 10) because it’s what we’re accustomed to. The vast majority of programs that output digits of pi do some in decimal.[a] But 10 doesn’t fit into our (well, Western) base 7 (common scale) or base 12 (chromatic scale) note system. Using pi encoded in base 7 or base 12 would make a lot more sense.

[a]: There does exist an formula to output any digit of pi (in base 16) without calculating any of the preceding digits: the Bailey-Borwein-Plouffe formula[0], but that’s not base 7 or 12. I do remember reading about someone generating the first trillion digits of pi using said formula and converting to decimal as it went along, so one could adapt that program to do base 7 (or 12) if they wanted.

[0]: https://en.wikipedia.org/wiki/Bailey%E2%80%93Borwein%E2%80%9...