Yes you can. Here's how. This text is not my own, so don't give me credit.
I've been toying with the music command. I finally figured out how you can play your mp3s in this game. First, create a zip file with a bunch of your favorite mp3s that you have downloaded. Call it music.zip or whatever the hell you want. Place this zip file in the base directory of the game and rename it from music.zip to music.pk3. Apparently zip files and pk3 files are exactly the same damn thing. This works, trust me. Now inside of the game, you can use the music command to change the background music to one of your mp3 files. For example, one of my files is lordsofacid-outcomestheevil.mp3. To play this I'd open up my console and type music lordsofacid-outcomestheevil.mp3 and the song will begin to play. Now you can whoop some ass to some awesome music rather than just the stuff the game came with.
This only works in MP. Enjoy!
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