Go to the steamapps folder where the game is installed. Download VLC or something similar that is capable of converting .wma files to .mp3 files. Copy all the original music .wma files from the Music folder so some place safe. Convert them all to .mp3 using the software you like to use. Rename the file extension from .mp3 to .wma. Put them back in the music folder and music should work perfectly fine.

Great game, the music is a must for the ultimate experience. The music fix is straightforward that takes 5 minutes of your time