Seems like you'd need to find someone who could create GBA sound format music for that though. Probably pretty uncommon.
I'm also not sure that the extreme use of grey in HoD was unintentional. It was probably part of the intended atmosphere, and HoD certainly has a rather unique atmosphere.
Actually changing the music wouldn't really be needed, I think. The problem with HoD's music is just low quality samples. That can be changed without messing with the music itself. As a matter of fact IIRC one of the palette upgrade projects for Final Fantasy VI also replaced all the crappy samples in the GBA version with the samples from the SNES version and it is infinitely better. So it seems like it could be done for HoD, too.
I'm not sure about how rom expansion works for GBA, but since those games *seem* to use a file system like most modern games it may not be much of an issue at all.
So how about replacing all the HoD samples with ones from SCV4 or CVDX? There are already programs that can rip the snes samples with little effort.
Speaking of hacks... I had an idea for a CotM hack.
My idea is to rework the game as a prequel for Bloodlines/PoR/OoE.
Rework the cast:
- Morris Baldwin -> Baldwin Morris, Quincy's grandfather.
- Hugh Baldwin -> Hugh Morris, Quincy's uncle.
- Nathan Graves -> Nathan Morris, Quincy's father.
- Hunter Whip -> Vampire Killer.
- And maybe... Carmilla -> Elizabeth Bartley, but not for the regular boss fight.
Remove Dracula entirely, and only show the coffin thing from OoE.
The whole thing will be about Carmilla trying to resurrect Dracula and she will be the last boss instead of Him.
The rivalry between Hugh and Nathan will be a bit deeper since they are now brothers, and Hugh will be ignorant of the price of using the Vampire Killer until after the battle against him.
And in the ending Baldwin will suggest taking Dracula's remains to an organization he knows of that is researching ways to defeat the Dark Lord.
Giving the graphics an upgrade wouldn't be bad either.