Victory gives way to agony in Crystal Towers 2 XL.

Today was an unquestionably good day for me in this game. The biggest bane of my CT2 experience, the Leaky Pocket challenges, were finally dealt with, all of the items in all stages were gathered, and every boss save for the Silent Void (this includes Megacarrot) has been defeated.

The only thing standing between me and 100% completion: 1 of the 25 keys.

As all 20 in the stages have been located, that tells me that it must be hidden in Music Castle itself.

The ones I have found there:
-The one used to show you what keys look like, under Luminous Towers A.
-The one on the ledge in the Walled Garden area, dropped down to from Azure Cliffs C.
-The one under Megacarrot, which you have to use the Launch spell and purposefully smash your head into the ceiling to reach.
-...And one whose location I can't recall.

I've searched Music Castle high and low, going through every spot I can think of multiple times, but I can't find the damned thing.

David, please...where is it? I'm starting to go a bit stir-crazy trying to find this damned thing. D:

It is done. :D

After a somewhat embarrassing revelation about that last key I was looking for was hiding (thanks again to ravenworks for inadvertently assisting me), I took on and defeated the Silent Void, completing my run at David's masterpiece.

I said earlier today that the feeling of conquering the "Leaky Pocket" challenges at long last would be better than the feeling of achieving 100% completion.

Boy was I wrong. :D