Not sure what the problem is. I lost my old disc a long time ago, so I have it torrented with all of the files. Everything works perfectly, the game runs flawlessly, and the BGM even plays during the opening sequence and menu themes, but during a mission, it's dead silent. This game is plenty fun, but I feel like it's missing the cherry on top without the awesome soundtrack. Any idea how to fix this?

Try to replace the Sound.rez file in your shogo dir. If that will not work the sound.rez file might be corrupted. Let me know if it works otherwise I'll upload the sound.rez on my tribute site.