This is what Drog Black Tooth wrote concerning the soundtrack:
By a stroke of luck, one of the few promotional CDs that were distributed in Europe for free was found.
The soundtrack was never released commercially, and all we had were the mp3 (128 kbps) version that Sierra made available for free download and the in-game version, which had the same quality. But since the mp3 files were available for free download, one would assume that distributing the uncompressed tracks is also legal, but alas Sierra never released them.
A few weeks ago I found a person (who preferred to stay anonymous) that had a promotional CD and was willing to share the original tracks with everyone. And now the Arcanum soundtrack is here, in all its glory!
The soundtrack has also been converted for the in-game use. While you can download the MP3 version (320 kbps), it's also possible to use the original wave tracks in the game with the help of a small patch.
I'd like to thank Mr. Houge for his magnificent and moving music. Only thanks to this fine gentleman we can enjoy such a unique work. He poured a great deal of love and attention into his music and it's greatly appreciated. I encourage everyone to read his notes and comments on the soundtrack
And most importantly, if you're interested in Arcanum and its soundtrack please consider purchasing a CD if the soundtrack ever gets a commercial release.