It sounds like cathedral music at first. Then, like modern classical. A drone of swinging chimes and rumbling gong is Swans' overture. Each tone is so exactly measured that, initially, it sounds like stock music pouring forth from the venue speakers. Look closely though, there to the back-left of the Trees stage, and you can see him, or it: a dark figure chipping away at a spectrum of percussion instruments. He looks slight at first, then the shadows slip off his back, revealing a muscled creature like human skin wrapped tight across the frame of a bull. This is a man named Thor, Swans' famed percussionist. He must've been cut from the same cloth as mythology's Hector.

The thunder of mallets continues as the bulk of Swans take stage and man their posts. We have the aforementioned Thor on percussion, a drummer, a lap steel guitar, a bassist, and, once frontman Michael Gira arrives, two guitarists. Just as the low-end percussive drawl plateaus, Gira advances, looking like he's fresh off a homicide. His hair is spindly and wet. His face, which he wears like a mask, is pinched and screwed, as if animated by a mix of rage and ecstasy. The effect of his entrance is like having a lion walk through your front door. The air pressure drops, hairs become needles and there's this fierce split struck right through the center of your everything. Cue the prickly strings: "Heeere's Johnny!"

With everyone in place, the atmospheric intro gives way to a rubbery, cyclical pulse. Like most of Swans' recent output, this track, a new one titled "Frankie M," moves about a central loping axis that sees the song always in the midst of either ascending or descending, expanding or contracting. It builds, then sustains, unwinds and recoils before closing. It's the perfect opener. So perfect, in fact, that it blows Gira's amp.

After a fevered snarl of "fucks" and "damns" from an angry Gira, the show continues. Up next is "A Little God in My Hands." It's off Swans' new album To Be Kind and straight out of the group's top shelf. A chimerical toss of graveyard blues, skronk and Gira's nasally growl, "A Little God..." is a display of how Swans has evolved over the last 30 years. Nowadays, there's less punch and more haunt, less frenzy and more funk. The structures are less cluttered, more minimal. That is until the inevitable break, when each track blooms out into cacophonous abstraction. Then It's like a seam ripped straight across the sky, every dark and frightful thing poured thick across your world. The sensations involved are both orgasmic and the opposite of orgasmic -- pain and pleasure rolled into one blinding burst.

And "A Little God..." has the mother of all instrumental breaks, a hellish squall of trombone, cymbals, tremolo steel guitar and bass that's as traumatic as it is euphoric. In the black panorama of the slam's midsection you feel like one of those doubled-over trees in old atomic bomb footage -- bowing down, broken, prostrate. As the audience eagerly laps up this bludgeoning, Gira sways back and forth on stage. He's rocking forward and backward, and with each inverse motion, he passes under the stage lighting and is transformed. His carnivorous eyes and thousand-yard stare remain intact, but his face -- one moment cloaked in shadow, the next bathed in light -- is a flickering sheet of weathered flesh.

As good as "A Little God..." is, "Just a Little Boy" is the evening's summit. Here we see Gira in all his monomaniacal splendor. One moment he's barking glorious nonsense, the next he's conducting with arms outstretched like a marionette Jesus Christ. All throughout, he does these wonderfully eccentric, free-form dance moves that should come across silly but don't; only Gira can make goofy ass-shaking and floppy wrist gyrations look genius. The strange manner in which he tosses his body about is, admittedly, both lithe and athletic. Hell, you could almost call it graceful. Even his flailing arms which, in their chaotic writhing, really do look like two eels trying to free themselves from his torso, exude an odd sort of elegance. Perhaps, it's because there's something terribly romantic about a man devoting his sole life to the lustful pull of his creative urges. Regardless of the reasons, once "Just a Little Boy" concludes, the audience, as they have all night, respond with boisterous applause.

The rumors are true. Yes, Swans live is extremely loud; at times, frighteningly so. But to say that's even the most obvious characteristic would be wholly misleading, a surface reduction of the emotional and aesthetic complexities that unfold when the band perform. The blanket of noise isn't even exactly painful. It's more aqueous than sharp, shrouding the senses in something akin to a haze. Which is to say, Swans live is an all-coloring sensory deprivation, like the stupor of a toothache or the fog of a weighty fever.

In this way, Swans functions as both an escape and a wake-up call. Maybe their unapologetic exploration of the bleakness of humanity -- the nastiest corners of love, sex, religion and power -- is one of the last great bastions of musical expression we have left. And maybe, just maybe, the most efficacious redemption of the human condition lies in exposing its ugliest appendages for all the world to see. If you buy that, then last night's show at Trees was nothing short of revelatory, and if you don't, then Swans simply put on a mesmerizing performance, a concert about as perfect as they come.