MDF for walls in music listening room

Ed: Why not have us design your room? Getting the material is not difficult, many building supply places have it or can get it. The trick is knowing how much to use and where. That's where we can help and give you a first class listening room using these types of basic materials--thus not breaking the bank.

I like OSB vs MDF idea and yes definitely use drywall to finish. Like Rives says you don't want to use too much rigidty and have the room not absorb.

If you have some specific question with detail I am able to give you some direction based on room dimensions and detail built into the walls. I will even do a basic RT60 calculation for your room with and without OSB/MDF and chart the axial mode that can be plotted for comparison against ideals. No room is perfect even after extensive planning and some tweaks are necessary. If your room is for HT the demand is less stringent because almost everything in HT is fake and loose, kinda like golden topping.

email me if you care to discuss

Rives - thanks for the idea - will take that into consideration and likely be contacting you in the somewhat near future.
thanks
-Ed