As I was saying, you can make a separate entry for the disc which is available separately (remix disc) but not for the one that is not and give the false impression it's also available separately.
If that was in place, there would be two separate entries for
The Witcher actual soundtrack and inspired by music even though you get them both in one package only.
Take note the Soundtrack got a separate entry because it was available separately
http://vgmdb.net/album/14195