I know other people have experienced this problem, but can't find a fix or an acknowledgement that it's being looked into.

I frequently get two different soundtracks playing in game, sometimes it's the Main Theme, which never stops from the character screen and bleeds into the rest of the game, and sometimes the Stronghold Theme does the same thing. Those are the ones I've noticed anyway.

 

The only way to fix it at the moment is to quit the game completely.

 

Confess it drives me slightly barmy.

Sadly the only way I have been able to correct this myself is to restart the game. I find that it happens far less often after I reset my PC rather then leaving my PC on for days straight.