If you're scanning about in search of the formal dining room, don't bother—there was one, but this family didn't want it. They all play instruments, so Smith turned it into a music room, which holds their Steinway piano, a chic graffiti painting by the artist Retna, and big, square midcentury chairs upholstered in black pony skin. Vintage Milo Baughman chairs in Caldelle Leather cowhide. Grand piano, 76 Steinway. Throw on sofa, Hermès. Art, Retna.