The (very good) main theme from Cold War Zombies, now for the main menu of another 4 player co-op game. Drop it into your overrides folder like you would with other music mods.
Credit to carl ruins everything for helping me slap this together, since my complete lack of experience with modding wasn't doing me any favors.
Please tell me if I screwed something up with downloading the mod since I have literally no experience with this.