I don't normally mod games in general, but I want to mod the normally unused song Pizza Mayhem into The Crumbling Tower of Pizza as going for 101% will still not have the entirety of "Bye Bye There" playing in a speedrun attempt of CToP, while Pizza Mayhem will just barely hit its loop as it's only around 3.5 minutes long.
It'd just feel really cool if that was playing on a good run so I'm really hoping the answer is yes. The mod in question: https://gamebanana.com/sounds/66594
Unfortunately no, we wouldn't allow it. Any and all mods to the game are disallowed for verified runs. That includes anything that replaces music.
You could, however, mute the game music and listen to your own music through other means. Just make sure game SFX is clearly audible.
We noticed that the rules did not specify that the ingame timer should display three decimals. This had become an expectation on our part, but it seems we overlooked reflecting this in the rules. This has been fixed.