Following on Dusk at Cubist Castle and its ambient dreamscape sidebar Explanation II: Instrumental Themes and Dream Sequences, the Olivia Tremor Control continues its lo-fi high jinks with "The Opera House," a quadraphonic odyssey in microcosm that pairs the titular psych-pop nugget with a 15-minute musique concrète experiment, then calls upon listeners to create their unique songs by playing back the tracks simultaneously in various temporal combinations on opposing stereo systems. The process becomes exponentially more interesting when the first half of the two-part "Opera House" single -- complete with a different yet similar musique concrète piece -- enters the equation, requiring a third CD player. (More interesting still is the double-disc vinyl single, which adds variable RPM speeds to the mix.) Similar in conception to the Flaming Lips' Zaireeka, "The Opera House" most closely recalls those old "Choose Your Own Adventure" books on which kids of the '80s grew up. The paths and possibilities it lays out are endlessly labyrinthine and completely immersive.