Whether you self-identify as a metal-attuned hipster or a hipster-hating metalhead, and whether you scan Pitchfork's reviews or prowl the message boards of the American Nihilist Underground Society, you've likely considered the shifting sound of black metal during the last decade. In recent years, the bands that have earned the most attention and acclaim have generally used what began as Scandinavian misfit rock to springboard into something epic. Wolves in the Throne Room's atmospheric bombast, then, aligns with Alcest's haunted dreamscapes. Deathspell Omega's mean psychedelic crunch links with the scorched expanses of Horseback and Locrian. Sure, plenty of recalcitrant bands-- Watain, Akitsa, the intractable Immortal-- adhere to decades-old, fast-blasting strictures. But from the keys and strings Emperor used to the sense of grandiosity Mayhem promulgated, orchestral elements and widescreen scope have consistently been part of knotty ol' black metal. On their fourth album, Portland, Ore., quartet Agalloch peerlessly unify both camps. As atmospheric as it is aggressive, as reliant upon old-school bona fides as on imaginative flourishes, Marrow of the Spirit confirms Agalloch's place at the frontier of American metal.

Marrow of the Spirit begins, as have each of Agalloch's three previous LPs, with a reflective instrumental. A forlorn cello moans over field recordings of a brisk stream and chattering birds, mixed so that each element feeds into the others. Together, they offer an image of melancholy, energy, and beauty that serves as a prelude in the most proper sense. Agalloch deals in light and dark here, moving beyond simple damnation and apocalypse to consider escape and renewal, too. Through a series of sketches and scenes, frontman John Haughm offers desolation and collapse-- "I slumber in clouds of ice/ These are my hands... so it is done," he groans during the opener. The next hour is a tug of war between retreat and rebirth. "There are gods in the wake of the very flame," he sings at the album's other end, placing his hope in a hopeless void.

The music here mirrors that message, a trait that requires dynamic, diverse, and compelling arrangements. Introduction excepted, Marrow of the Spirit's five tracks range from 10 to 18 minutes in length, and, more often than not, one marathon simply segues into another. Though the album breaks well past the hour mark, Agalloch couple economy and pacing with imagination and ideas in a way that should make most black metal bands green with envy. The 12-minute "Into the Painted Grey", for instance, maneuvers with enough agility that its runtime feels appropriate. It transitions from ascendant guitar solos to relentless, howling stampedes, twisting the two again and again into blissful terror. A barely audible 12-string acoustic guitar laces much of the track, adding ballast to the blast. That guitar serves as the bridge into "The Watcher's Monolith", itself a perfect distillation of the breadth that's made Agalloch matter for the last decade. Spider-webbing from folk-rock smolder to mid-tempo thrash, from hair-metal guitar workouts to dirge-like chants, "The Watcher's Monolith" plays like an unpredictable, seamless mixtape of Agalloch's strengths.

And that's the key: Many of Agalloch's peers in bending black metal manipulate it one way or another, then simply revisit, retread, and retrench. For Agalloch, though, black metal is just the thread that ties together dozens of different looks, be it the industrial roar and mid-tempo climb that characterize "Black Lake Niðstång" or the saturating sustains that spread from one end of closer "To Drown" to the other. "Ghosts of the Midwinter Fires" sprints and twists like a lost take from Maserati or Mogwai, its chiseled guitar line leading the way through sharp turns. But just as Alcest did on this year's excellent Écailles de Lune, Agalloch almost always retain a stylistic placeholder, be it rolling blast beats or Haughm's lacerated exhortations. Black metal, then, becomes a compositional catalyst, not a stylistic restraint.

Agalloch don't tour much, picking and choosing their tour dates and bill-mates based on what they find interesting. In March, they flew to Romania to play two shows with Alcest for free, though they've barely played within their own country at all. The band seldom offers interviews, either. "We believe in having a spectacular experience rather than touring constantly and making a lot of money," Haughm told a Brooklyn Vegan writer who made that trip to Romania, too. "We're not interested in hype, or all this rock-star bullshit. We're fine if we're at an underground cult base forever." Similar ideas have cultivated audiences for the formerly hermetic songwriter Jandek and veteran masked emcee DOOM. But black metal itself has started to seep closer to mainstream culture, both through its influence on other artists and in acknowledgment from big media outlets. Agalloch's cult status might not be so safe, then. On Marrow of the Spirit, Agalloch successfully springboard from a foundation of black metal to an intriguing sort of polyglot rock that never seems contrived or forced and always surprises. Very few records sound like this-- yet, anyway.