I think you aren't respecting the sound meter like every other one who get stuck on the final phase, It's on me though, I should have explained that mechanic better, my bad! , when the sound meter is over 40% to 60% the sound character will get angrier and start progressing towards you, when it's 60% he will start getting progressing much faster, so try to keep it less than 40% :D
I was definetly watching the sound meter religiously! I think I got continuously killed by the pumpkipider one, it's so hard to find him sometimes and when I get to the final door it's or too late or i've wasted ALOT of time just running around and waiting for the Bubbly one to disappear or something...
Didn't really have trouble with the sound mechanic accept for it being another thing I have to wait for to continue (next to waiting for the flash to refill etc.)
*Still loved the game overall though! The vibe is there for sure.