I have done two sound rooms in acoustic fabric. The first in Burnsville, MN and now in Woodbury, MN.
This material is available at any high quality paint and wallpaper store. It comes in a variety of colors and textures and goes up like wallpaper. It is about 1/8 inch thick and does an excellent job of taming high frequency reflections. The rooms I treated went from sounding like unfurnished suburban "boxes" to dead quiet and very listenable.
I also did the ceilings with the thinnest Sonex acoustic foam panels and thick wall to wall carpeting. In my present room, the acoustic wall fabric was about $700 installed and the Sonex another $700.
It really works well. Call me and I can give you an over the phone "knock, knock" test. 651-330-9871