The August Wilson Center for African American Culture is the perfectly delightful, almost cozy setting for two Pittsburgh premieres and a world premiere presented by Pittsburgh Ballet Theatre dancers. Uniting the three B's of classical composers -- Brahms, Beethoven and Bach -- with three acclaimed contemporary choreographers in Dennis Nahat, Mark Morris and Dwight Rhoden to produce "Uncommon" is another feather in his hat for PBT artistic director Terrence Orr.