Heard in the wake of their near-flawless debut, the later Mars Volta discography can feel like a thicket of hyper-indulgent rabbit holes. But on Octahedron, they recaptured the focus of their earliest days on a set that perfectly balanced avant-rock info overload with psych-folk mysticism. As brilliant as Cedric Bixler-Zavala was right from the band’s inception, there may be no better showcase for his enormous vocal range than this LP, whether he’s locating the strutting R&B attitude within the crushing neo-prog of “Cotopaxi” or flexing his androgynous falsetto on an enchanting ballad like “With Twilight as My Guide.” In their middle period, the Mars Volta could sometimes sound frenetic; here, they seem utterly relaxed in their staunch eccentricity and improbably broad range. If De-Loused in the Comatorium will forever stand as their masterpiece, Octahedron sits beside it as a reminder of the depth and richness of their full catalog.