Looking at the picture I can pretty much deconstruct how the talented
Erskine group did the wall panels. I'm stuck in my office today so I will try to describe the general approach. Dennis's guy may have used different methods/materials but you should be able to get similar results using this approach:
Starting with a flat drywall surface you will build all the panels on the wall
Mount 1 inch thick furring strips to the drywall with liquid nails and drywall screws around the perimeter and directly under the location of the decorative molding. Plan the furring to support the crown molding at the top and the baseboard at the bottom. Multiple parallel strips may work best for the baseboard.
Mount a 1 inch thick mounting plate to the wall for the sconces at least as big as the sconce footprint.
Attach a combination of linacoustic, batting or other 1 inch thick wall treatments to the wall per your overall pre-engineered acoustical treatment plan fitting pieces between all the furring.
Stretch and staple fabric to the furring strips. Plan the staple locations so that they will be hid by all the trim work and sconces. I would use a full size cardboard or foamcore template as a stapling guide.
Fasten all the pre-finished
molding to the wall hiding all the staples with finish nails.
Touch up nail holes, mount sconces.
You can buy pre-curved molding, or make your own. I don't think flexible molding was used. Dennis's team may have wood bending capability. You can google wood bending if you really want to go down that path, it would require a bit of learning and equipment. Here is one source I found doing a Google for curved case molding: http://www.curvedmouldings.com/curves.html
Here is a video on steam bending wood for you to get an idea of what is involved: