 Three of the members of the String Theory Quartet, violinist Ruth Lenz and Jessica Escobar, and cellist Johnny Lenz. They and violist Dustin Budish, the fourth member of the group, perform tomorrow at 6 p.m. at the Quad at the University of Nevada, Reno. It's a free outdoors performance, part of Art Town's Art Town on the Quad series, and features both classical and popular musical selections.