Lela and I have been collecting music from games for years and placed both the theme music and other music from about 40 games onto our MP3 players. Such as the theme of Maniac Mansion, the song Freddie Pharkas sung by Al Lowe, the beautiful music of Syberia (including the song sung by Helena), Journey to the Center of the Earth, Atlantis II and many more. We play them often. Quite a large number of games had their music end up on CDs. Most were available in Europe. I'll have to see if I can make a list of them for you collector's out there. Here are a few that I can remember.
Myst III, IV, V and URU
Zork Grand Inquisitor
Return to Zork sountrack is on the game CD
I'll see if I can put a complete list together of the CDs I know of and also a list of Websites where you can download some game music. GOG also provides some game music for some of the games they sell.