Some years ago, Michael Gira’s Swans rattled (literally) Kenmore Square with a bass-boom earthquake of a show at the Rat. Their opening chords shook the stage at a molasses crawl of about 2 bpm before working up speed to a slow-dirge finale that, by comparison, seemed a speed-metalist’s dream. The mechanics are different, but on SGNL>05 Boston, heavy-music quintet Isis create the same visceral effect of a sonic ascension from Hell to Heaven, with a pit stop in Purgatory.

A jarring EP of epic-minded mini-suites, SGNL>05 coldly scrapes and scratches its way up through funereal trudge and chain-gang pound with a roguish glee. "Divine Mother," a firestorm of guitar crunch and bottom-crushing beats, sounds like a guttural SOS from inside a blast furnace. A fierce kick drum leads "Beneath Below" in a somber, accelerating march of speaker-ripping low end and percolating waveforms. Slow-burning riffs are hammered for every drop of blood, and the vocal passages twist truly tortured emotions. But ultimately, with well-placed textural and rhythmic relief, SGNL>05 isn’t about pain but the release from it. And when the disc hits a remix by Godflesh’s Justin Broadrick of the title cut from last year’s Celestial, the escape is topped off with a gentle rush of chordal bliss.