Something I've noticed is that if you play the music from the sound menu in the options screen, you cannot stop it playing. The stop button won't work.
Also, when the mission has been completed it continues to play until the in-game section of the next level. It will then switch tracks like it should.
I also have TA on CD (but no expansions) and the stop button does work properly.
It could just be me so I'll see how this goes.

Noticed the same issues, nothing we can do about that I guess.

I can confirm the same issues with the soundtrack.

Yep.
I'm getting this.
Still better than nothing.

TA was always bad with the sound track, what we used to do during our epic games was to turn off the ingame music and fire up a media player in the background (you can even add the TA sound track to your media player if you like ^.^)

better than Impulse version, in which the OST does not work at all, and costs 10 bucks (and I bought :( )