Ralph Lemon may be the ideal Walker Art Center artist in that he defies categorization on principle, blending dance, performance, visual art, text and music with a hallucinatory sense of form and structure. Lemon calls his new combination performance/ installation, Scaffold Room, a “lecture-performance-musical” in which modes of contemporary performance are “refracted” through the archetypal personas of black women in American history, fiction and popular culture. Sept. 25-28, Walker Art Center, 612-375-7600, walkerart.org