Twyla Tharp: Unceasing quest to reveal truth in human movement

To celebrate a half-century of making dances, Twyla Tharp has done one of the most difficult things a performing artist can do. For her anniversary tour, which landed her and her dancers at the Kennedy Center Eisenhower Theater on Wednesday, it's not so much her creation of two new works -- both high-energy, deeply musical and engaging -- that is extraordinary.