Just do some cardio and make sure you're eating before and after the rave sessions. Drink lots of water, and if you really want to get silly with it, get some aminos to put in whatever you're drinking. 4-5 hours of dancing isn't going to threaten your muscle mass as long as you're eating enough to compensate for the calories burned.
If you're really "really serious" about building muscle, don't dance for 5 hours. Get in a workout or eat something instead. You can't say you're dedicated to putting on mass if you aren't willing to sacrifice fun stuff in the name of getting bigger.