I am also in the process of constructing a listening room, and am installing wood floor over slab. Out here in the Pacific Northwest, we like a moisture barrier over our slab, so this is what I am doing to install my floor.
1) Clean slab and paint with a sealant. In this case I am using a product by AFM-Safecoat, as it is non-toxic (non stinky) and the slab room is already enclosed as part of my house.
2) As an added moisture protection, I am laying 60 mil plastic sheeting, a single piece.
3) I purchased 2x6's and ripped them down to 2.25". They will be used as sleepers for the floating floor.
4) I purchased 2" thick foam for insulation, and will rip that down to 10.5" wide slabs to place between sleepers. This will give me a 12" spacing.
5) Floor goes down - 0.75" tongue'n groove, bringing the new floor up to 3" above slab.
The main reason I write all this is to advise about the moisture barrier. Plastic alone will likely do. But if you want more, be sure to use something that is friendly to your indoor environment - not something like asphalt foundation sealer (which really stinks!).
