+ T back at you!
There is a product that is being used now in new construction home theatre rooms for noise cancelation that goes under the drywall. If I remember right it is a rubber-ish strip that goes over each stud/truss/rafter that has drywall attached to it under the drywall. It is supposed to do a lot to cut down on vibration and thus deadens the room. I will talk to our audio install company and find out what it is called. I'm a salesman for a homebuilder btw. I don't do a lot of houses with
highend med-highend audio rooms but I do a few. Anybody ever heard of this?
I've also heard of using a layer of 1" r-board under the drywall. R-board is typically used on the outside of the home for insulation. It is very rigid foam, and drywalling over it isn't a problem as long as you use long screws, and mark where your studs are on the foam so you don't shoot a million in without hitting wood.
Just for general building practice, regardless of what you do for sound. It would be a good idea in that room to use steel angles where the rafter hits the side walls. Rafters and trusses move quite a bit with changes in temp and humidity and that is how you get a lot of split seems at the corner of outside walls. The idea here is that the steel angle (very thin steel specifically designed for this purpose) attaches to the wall, and instead of attaching the drywall to the ceiling at the corner, you screw it into the stell angle. then the rafters/truss can move without pulling on the seam. surprisingly not all pro's use this, and we have to specifically ask for it when we get a new drywaller. Once they understand how much warranty work it saves them, they never charge us for it.
matt