CedricBusch: I am guessing Isles is same. It seems (early, quick overview) the .sav files use the same structure and hashing algorithm as Xeen -- I am not sure about the .cc file. Either way, the tricky part will be figuring out the original music file names. I am currently brute forcing the XOr value to "decrypt" mm3.cc.
It's not the same. The structure is very similar, as you said, but like I said earlier, the encryption isn't understood. I've already brute forced through every xor value and none of them return anything meaningful.
I've attempted some white box reverse engineering on MM3.EXE, but it's an intentionally obfuscated mess. Unlike MM4/5 where the "file" within the CC can just directly be XORed and dumped, there is some algorithm used in MM3 that I don't understand. The first two bytes of the file pointed to by the offset are not actually part of the file, they are the seed to the algorithm. From there, it becomes a mess of adds, shifts, and XORs. The actual files starts at offset+2.
If you're handy with a debugger/decompiler, I can send you the uncompressed EXE.