PowerLESS delights in the teeming, multifaceted world of Stravinsky's beloved "absolute music": music with no external, explicit "meaning." Two compelling musical edifices bookend a marathon program that traces a hypnotic path from darkness into light. The Armory's vast drill hall descends into darkness for Georg Friedrich Haas's otherworldly, hour-long in vain. Circling, spiraling wisps grope their way through the cavernous dark, searching "in vain" for safe musical home. Steve Reich lets the light shine in, as his Music for 18 Musicians, a pulsating, joyous ode to musical abstraction, leads listeners on a mesmerizing musical road trip. An inventive arrangement of J.S. Bach's elaborate miracle of musical construction, the D minor Chaconne, introduces and leads directly into Reich's work. Speaking with a still small voice between the twin monuments of Haas and Bach/Reich is UrSonate, Kurt Schwitters's uncategorizable work for solo speaker, which makes compelling musical drama out of an invented, nonsensical language. Steven Schick's virtuoso performance is the stuff of legend.