Seldom has an album come more squarely out of nowhere, or with a better legend attached, than Bon Iver’s debut, For Emma, Forever Ago, released in May. The story went that Justin Vernon recorded its nine songs over three winter months alone in a log cabin in Wisconsin; that he’d retreated from the world to pick up the pieces of a life that seemed to have fallen apart; had gone with no particular thoughts of making an album, yet had come back with this. Our own Mark Edwards called the set “a minimalist masterpiece”, and his review was one of the more restrained. No wonder Vernon chose the name Bon Iver - a corruption of bon hiver, or good winter.

Wisconsin is a northern state, known for logging and hunting and corn, but Vernon is no redneck: he studied world religions before moving to North Carolina in search of a break for his band, DeYarmond Edison, in 2005. When the break didn’t come, the band collapsed after 10 years together, prompting Vernon to split with his girlfriend and return home, feeling rudderless and lost. Web rumours posit For Emma as an attempt to win his girlfriend back, but Vernon insists that the reflective melancholy in his songs relates to something more timeless and complex, saying: “It’s centred around an ancient, long-lost love. But, as happens in people’s lives, old relationships often have plenty to do with new relationships as they come along ... it’s telling a story of one lost relationship and how other ones collided with it.”

The extraordinary feature of this tale, and the thing that makes tonight’s sellout show such a strange occasion, is that nothing in Vernon’s musical background could have prepared either him or us for the sudden ascent that brought him here. With his old band, he’d sung in a gruff baritone, but alone, over that winter of 2006, he discovered a delicate falsetto through which to channel his gentle swirl of emotions. The cabin in which he lived had been built by his father in 1979, so there was a sense of coming home to reconnect and explore as, with the temperature reaching -20C outside, he chopped wood, shot a deer to keep himself fed and began to record with “the junky old stuff” he’d brought – chiefly, a baritone guitar, two drums, a horn and a reverb pedal. The result is an album of staggering intimacy that seems not so much to hook as possess its audience.

Which goes some way to explaining the sense of fervour inside the Empire, the like of which I’ve never seen directed at such a newly discovered artist. If the crowd was expecting to turn up and simply bathe in the music of the album, however, those expectations don’t last long, as Vernon, accompanied by a bassist, a drummer and a second guitarist, seats himself on the right of the stage, leaving the centre empty, and launches into an unexpectedly robust version of one of the album’s highlights, Flume. Burly and tall, sporting a check woodsman’s shirt and ’tache, the singer needs no more than the feedbacking wig-out at the end of the second number, Lump Sum, to establish that his songs will not be treated as sacred, and that the intimate hush of the album is for home consumption only. Shortly afterwards, the sweet pulse of Creature Fear finds space for a Pat Metheny-style guitar solo, while its follow-up, Blood Bank, is a beefy, generic rocker not included on For Emma. All receive ovations that are no less bewildering than the arrangements.

On the one hand, Vernon’s desire to confound expectation seems laudable, but it’s also frustrating, robbing his songs of the singularity that makes them so emotive. Only when the backing musicians exit, leaving him alone to perform re:Stacks, one of the most stunningly beautiful songs I’ve ever heard, and pretty much everyone’s favourite from the album, does an explanation for all this tinkering present itself. Accompanied by a chiming Les Paul, re:Stacks’s plaintive melody would be enough to entrance a pit of cobras, and needs no adornment of any kind, yet Vernon can’t resist embellishment. He doesn’t yet trust the song, as though it really has come from somewhere else and he needs to wrestle it into submission. A short while ago, the singer described receiving an e-mail from a man who’d been playing For Emma to his terminally ill mother, and went on to observe: “The music seems to be doing something for people in a serious way ... I’m really happy, but I don’t know how much I have to do with it.” Of the album as a whole, he has admitted to a sense that “I can’t take credit for it, and I was the only one there”. What a peculiar feeling this must be.

The set proper ends with audience participation on the previously plaintive The Wolves, only for the magic to return during the encores on a shimmering cover of a Sarah Siskind song called Lovin’s for Fools, performed on acoustic guitar with massed backing vocals from the support band - and echoing one of the show’s other highlights, a spare, piano-based cover of Graham Nash’s Simple Man.

Standing ovations at gigs are rare, the more so at such patchy ones as this, but the response, one suspects, was more a way of thanking Bon Iver for For Emma, Forever Ago than for the show itself - a measure of just how loved the record is, and perhaps also an acknowledgment of how fast this has all happened for Justin Vernon. If he needs time to grow into his own work, that’s okay - he’s earned it. Let’s see what happens next time.

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