When Omar Rodriguez-Lopez and Cedric Bixler-Zavala silenced At the Drive-In in the midst of its popular emergence, there was no question that the two artists would return with new music as exciting as their previous band. However, there was plenty of discussion in corners and over drinks about what, exactly, that music would sound like. It was clear that much more was happening under those Afros than biting, post-hardcore anthemics laced with psychedelia. In 2002, Rodriguez-Lopez and Bixler-Zavala returned with the single "Tremulant," attributed to their new project, the Mars Volta. Its shifting soundscapes were certainly a hint, but with the Mars Volta's ambitious De-Loused in the Comatorium, it's clear the ATDI expats' mushroom-headed hairstyles hide bulging brains that pulsate with ideas, influences, and a fever-pitch desire to take music forward, even if they're occasionally led too far afield for the audience to follow. A concept album of sorts, Comatorium is a swirling ten-song cycle inspired by Julio Venegas, a childhood friend of the band who followed his fearlessness to a self-inflicted end. While the storyline is bewilderingly obtuse, it nevertheless unifies the album's wildly shifting sounds. Thrumming, Led Zeppelin-inspired pounding gives way to the thump of a free jazz bass punctuated with blasts of guitar squelch in "Drunkship of Lanterns." Meanwhile, the windswept landscape of "Roulette Dares (The Haunt Of)" unfolds over seven minutes, revealing remnants of ATDI, fissures of glittering, confessional pop, and layer upon sedimentary layer of a shrieking Bixler-Zavala, harmonizing with himself over vintage 1970s organ. All of this gives way to a gentle landslide of an outro, where an expressive guitar solo that would make Carlos Santana scratch his head threads its way between brooding bass. Later, Red Hot Chili Peppers secret weapon John Frusciante stops by for "Cicatriz ESP," which undergoes a full stop after its relatively straightforward (for these guys, anyway) beginning, reentering the atmosphere to the fiery strains of at least three concurrently soloing guitarists. Though the brief-by-comparison ATDI-ish "Inertiatic ESP" acts as an opposite to the epic "Cicatriz ESP," the band's ardent desire for re-creation is defined in the latter song's shifting folds and faults. But while De-Loused in the Comatorium may well remove the stigma from the prog and art rock forms it suggests, and is certainly a monument to unbridled creativity, it can also be seen as bombastic and indulgent -- much like prog has been in the past. Comatorium is exciting, to be sure. But in a way, it avoids answering that old question about the Mars Volta: What will the music sound like?