Final Fantasy XI (X360) scd encryption by bnnm at 1:01 PM EST on January 7, 2017
Maybe some experts out there can help out (not really needed, just for fun).
The game is using some early/simple .SCD header and the data seems encrypted.
I think it's XMA with a RIFF header and some kind of XOR'ing, and at 0x14 I suspect is the "key". Several files use the same key and the first bytes would match a "RIFFxxxxWAVEfmt ....". Also XMA typically end in series of 0xfffffff, which files with the same key encrypt consistently.
Some samples: https://www.sendspace.com/file/lt38ch (full set at joshw)