Title is fairly concise since I've taken the time to test, and it is in fact CelesteTAS causing this, and it has to be one of the 2 most recent updates.
The bug in particular only happens when the right direction is being held on the right analog stick. No other directions, and not the left analog stick
#CelesteTAS bug, where holding the right stick mutes all sounds
tame thunder
I don't know who to ping for CelesteTAS, so if someone could, I'd appreciate it 
sleek pawn
holding right on the right analog stick is supposed to fast forward during tas playback, and it's intended that fast forwarding mutes all sounds
however this happening outside of tas playback sounds like a bug
@abstract pivot
abstract pivot
yeah ive noticed there are some conditions assumed to be true, which i didnt account for
lament crown
however this happening outside of tas playback sounds like a bug
i think this- yea
i think this is related to the keybindings being weird