On stage at Koko a man plays flamenco on a classical guitar. Y'know, it's so lovely, so luxurious. It's like I'm 1980s Alfred Molina, or some sort of communist painter in Franco-era Spain, or, y'know, a Portuguese conquistador tasked to enslave indigenous peoples in the name of Catholicism. The artist, mischievous anti-guitarist Richard Bishop, completes his set, to a healthy round of applause "Thank you," he says, before adding "...and Swans are going to FUCK your insides." Well there you go, we cant say we weren’t warned. Let the fucking begin, I say.

Part 1: Day

Every square inch of this vertical labyrinth is taken up by people craning for a view. I finally find a spot four storeys above the stage, secreted behind a side pillar with one eye peering out through a keyhole of viewing space. This is fucking ideal, because very soon Swans will blow through Koko in a fashion I find difficult to fathom, and clinging with one eye in view to this red plaster I'll be the kid peering into the adult world through a crack in the door, witness to some midnight bedroom scene and a violent hunger I don't yet understand. To be honest, I'm sort of appreciative of this pillar, though, and I get the hunch I'm not alone in my trepidation. There's a definite mood of twitchy breath-holding as Swans come on stage - that weird energy when a couple of thousand people, staring and motionless, suddenly go quiet. The same eerie feeling of waiting that Alexis Petridis described at their gig in Koko, two years ago.

Waiting, yes, but for what? The fear we're entering uncharted waters isn't helped by the fact that opener 'To Be Kind' is a new song, or that it plies a Morricone-style ominousness - all rattlesnakes before the Mexican standoff – for the best part of an hour. It's more campfire hymn than song. Soon enough, though, the set erupts with one of their numerous SLAMS – every time the sound of angels singing; an airliner in vertical free-fall. And then it's from here, to eternity, that the band begin to move, in a trajectory that's simultaneously static and ever-ascending like the mythical Shepard Tone - what musicologists describe as a 'sonic barber's pole'.

Three hours, only seven songs, no folkies, no mercy.

'Avatar' is its own first act. The fastest track on the album is now its most biblically interminable. What begins with an expectant march of insistent bass and church bells, gradually mutates into something like a horseback charge into hell. "Your life," croaks Gira, "is in my hands." 'The Seer's opening perma-squall forces a blankness into your mind. It resets you, so that for the next 45 minutes it can make you, over the course of a dozen suites, a dozen different lives, and on through to the finale to end all finales. There simply isn't a rock song like it. "I've seen it all, I've seen it all" chants Gira, taking the words right out of my mouth. The other new songs, 'Nathalie' and 'She Loves Us' are hugely impressive; the former a mechanical sea-shanty caked in hysterical white noise and the latter a big lumbering doom rocker, Swans-style. It's the beast of the set. My God, the sheer weight of it.

The album songs are unrecognisable, mangled and masticated into new forms. All except one – 'Coward', a industrial citadel in a sea of oozing awe. From the backlot of 80s Swans, it's a caustically sheer halfway point to the set. The dead spaces between its 1-2-3 expulsions suck the air from the room. There's just a nothing - a pin-drop silence highlighting the crowd's absolute rapt obedience. This is the power of an impossibly tight band. Into these spaces slithers Gira, begging to be penetrated, to be loved, while a delay effect makes infinite the last words of the central refrain.

The twist is, while the longer songs appear to be all improvisational and freeform, in reality they are every bit as meticulously programmed as 'Coward'. It'll be a cold day in hell before Gira helms a jam band. Every note tonight is there for a reason, part of the greater machine, the master plan, the overall journey. As Gira is at pains to repudiate, Swans are labelled nihilist. But live, that couldn’t be further from the truth. Because, here they are building. It's all about the collectivist struggle: these new Soviets and the cult of disciple and toil and self-mastery, all for the greater good and the utopia. The utopia of musical nirvana, or spiritual transcendence, or just forgetting about your shit job for a couple of hours. Every downstroke requires an aching physical exertion and every rhythm-as-lead thrashing is drenched in sweat. Every bass string is pulled with the biceps, and every drum beat struck with Herculean intent. While their sound is a group effort, a hive-mind deal, every member's individual personality is distinct within the machine. Inevitably though, Gira's voice dominates.

Part 2: Night

There's a theory in modern cosmology that shares uncanny parallels with ancient Hinduism, and is in a greater sense, considered the point where science and religion finally intersect. The theory, that the universe 'breathes', the theory of 'space respiration', follows that in cycles of 16 billion years, or half 'exoseconds', the universe expands, then duly contracts. And yeah, it has a lot to do with the good old Big Bang Theory.

Perhaps due to the continued popularity of elbow patches, lab-pure acid and Floyd's Ummagumma, for a long time scientists have wrongly presumed that the nothingness between space matter was the colour of absolute darkness. But then in the 70s radio astronomers discovered that these voids contained a strange glow; a kind of radiometric background vibration, or quite literally, the sound of the universe. Soon after, observing that the wavelengths of these glowing voids were elongating, scientists deduced that the universe was in fact expanding. Or rather, it was contracting. As which point they were like, "Dr Dexter, skin us up a fatty boom batty 'cause we're all doomed."

The scientists then did what scientists do and quantified the radiation (at a temperature of 2.725 kelvins, just so you know) but to this day the source of the hum remains a mystery. Hindu theologists, however, pointed to the sound as evidence for the existence of God. This vibration, they said, was in fact the 'Om'. Case closed, we win, crank up The Beatles, I am the octi-limbed King of the Lotus.

Still with me? Ok, well according to Hindu creation mythology, from the navel of Vishnu (the 'preserver of the universe'), was born an egg. Out of this egg came Brahma, whose first sound on earth was 'Om': believed to be the 'origin of all creation', and known also as the preserve of every art-fucked drone-rocker in history, from John Cale to tonight's heroes, the six fallen sons of the anti-paradise: Swans. Anyway, what in Hinduism represents the 'ultimate truth', the Om, brings into life 'demon-eating' badass, Shiva. A being of 'neither birth or death' and the supreme male power of the universe, he is the destroyer of the universe to Vishnu's preserver (these religious types are all about equilibrium). It's then that Vishnu's brood of mini universe-makers will exhale, so creating the universe, and then inhale, so taking it back, the complete cycle lasting 100 'Brahma': the life-span of a universe. With the inhalation complete, and the universe partially destroyed, in comes Shiva to finish the job. This is the subject of Swans' The Great Annihilator, in which Gira reminds us that time is relative because time is cyclical, and that in the end we will fall "right through the wall of the place where we were made / right into the open mouth of The Great Annihilator." And so it goes.

I'm always deluding myself into mistaking technical mastery for real magic. It's a bad habit. To quote a totally excellent Paul Thomas Anderson film: "It's dangerous to confuse children with angels." I can't help it, though - i'm a big fucking bullshit balloon ready to pop with hyperbole, always ready to BELIEVE, as Taylor Parkes once wrote incredulously of The Stone Roses. I know this about myself, yet still I fight the urge to go full Julian Cope here and claim that tonight, in some or other version of reality, Swans literally do wield the power to create and destroy universes.

But I won't. What I will say, though, is that at the time and in a very real sense, it seems that way. It seems that way, when deep in the belly of the beast, as gradually I'm losing all my perspective to a force so preternaturally powerful that, after a full three hours in the company of what is surely the world's greatest live band, so difficult is it to make empirical sense of this experience, let alone articulate it, my only recourse is the metaphysical.

We're talking about wave after wave of a sound both damaging and hallucinogenic, that only becomes more difficult to articulate when adrift in the set's vast mid-section, following literally hours of simply mind-altering terror. By which point, and with the added consideration that, for an hour now, the harsh stage lighting has given Gira's sagging features the appearance of a fucking weeping statue, I'm ready to believe in near enough anything. I'm ready to believe that that within this frozen tenor of drone, with not a chord-change in sight or a moment's respite, really does reside the ultimate truth.

I'm ready to believe that, in time with this grotesque display of male power the universe is expanding and contracting, throbbing like a heart to the rhythm of a brilliant violence at its new axis. I'm ready to believe that, as adrenaline floods my body and I begin to breathe hard, I too am breathing in time with the universe. And also that, as Swans' sexual maelstrom heaves and retches and strains towards oblivion, we're breathing together, somehow attuned to that cosmic cycle of formation and annihilation.

I'm ready to believe that the set's extreme length is a conscious effort on Swans' part to recreate the conditions of an eternity. With their 9:15pm start now a distant memory, and as 10pm becomes 11 and I fall through ten minutes of single-figure repetition, the impression is of a music of neither birth or death, like a god. A sense of circularity that, you might say, renders time relative. Their music is always moving but never arriving. It's always dying but never dead, like the cowboys of Peckipah's slo-mo violence - old men frozen forever in celluloid, their blood-splattering falls time-stretched into abstraction. It's as if the New Yorkers are lodged in some cosmic bottleneck, between life and the afterlife, ricocheting between the two points of a two-note guitar loop, like a celestial glitch.

I used to think Swans were all about immortality. Now I see that for most of his adult life, Gira has been preparing for his death, or rather the moment of dying. Preparing for it by living it, or rather re-living it, endlessly, through his music. Their music inhabits this future memory, the precise point of soul evacuation - a second that lasts a thousand lifetimes, as in the perpetual ecstasy of metempsychosis you are for one single moment neither of this world or the next. Every single repeated unit of their minimalist drone is another return to that future memory, and we are suspended there. This is the way it goes tonight. That is, until the very last note of the closer 'Apostate'. During which, in a virtuoso tone-shift from ugliness to beauty, three hours of ruinous cacophony culminates with a single sweet note of peaceful resolve. And it is then, as the scriptures did foretell, Michael Gira breaks on through to the other side, and so achieves absolute dissolution, in the presence of the light. And the universe goes kaputt.

So I suppose that, in the end, I'm ready to believe in Michael Gira. Who, when he isn't spitting or yawping or scat-singing black magic into the mic, is talking to himself, over guitar, in a manner of a math genius in a padded cell, doomed to forever be unriddling the unsolvable equation that put him there. He is mesmerising to watch, a thing of pure old-fashioned charisma. Twice he refers to us as "his children," like we are his flock and he the good shepherd, and in a crucifixion pose he conducts his symphony of cruelty with an invisible baton. Here is a man who, for thirty years now, has been howling into the void, but who in 2012 burns brighter than ever. He's the eternal child, working miraculously at the top of his game at age 58, and I'm ready to believe. I believe that the grand narratives of rock's history live on in Swans, and I believe Gira when he tells us that The Seer is really about childhood, or put another way: death and regeneration.

I also believe I've had my insides royally fucked.