Jónsi Birgisson is a strange man, though not in the way you were expecting. His band, Sigur Rós, are essentially JRR Tolkien's idea of what an art-rock group should sound like – there's lots of windswept droning and shrieking but it's hard to listen for more than 10 minutes without thinking 'elves and hobbits!' Consequently, Birgisson tends to be pigeonholed as eternally star-crossed, a moonchild with a Tintin quiff and faraway gaze. You imagine him living in a cave above his home town of Reykjavik, carving runes on the floor and knitting interesting keepsakes from llama wool.
Actually, he's sweet and funny and, judging by our several encounters, comfortable in his eccentricities. He watches Game of Thrones and The Simpsons, drives around Reykjavik with David Guetta pumping at maximum volume. After Iceland's economy disappeared into a volcanic rift in 2008, he responded in the same way as all his neighbours: took out his pots and pans, walked to the national parliament and raised a ruckus until the politicians came out and faced their people.
The thing that strikes you immediately about him, however, is his distinctly off-beam humour. In the middle of a thought, Birgisson will stop and giggle. Slightly on edge, you may start to laugh also and suddenly there the two of you are, chuckling wryly for reasons that are entirely unclear. He insists he is no longer the media-dodging recluse of Sigur Rós' early years when, surfing a swell of critical kudos, the band straight-up refused up to talk to journalists.
Still, now and then you sense a sarcastic undertow to his answers that you just can't quite catch. So yes, he's engaging, yet with the capacity to unsettle you a little.
He was reluctant to do this interview and had to be cajoled by his label. His hesitation is understandable. Sigur Rós have, by their sedate standards, been through a period of upheaval.
After a decade of dramatic success – their graceful anthem Hoppipolla became internationally famous as the soundtrack to the BBC's Planet Earth – in 2009 Sigur Rós suffered the first of a sequence of wobbles that would soon put their future into question.
It began with Joni's decision to embark on a number of side-projects, including his transcendent solo effort Go (a love letter to his boyfriend, the New York record producer Alex Somers). Inevitably, rumours followed that Sigur Rós were poised to call it a day (exacerbated by Jónsi's chilling announcement that the ensemble was going 'on hiatus').
When they did reassemble, they were down a man, keyboardist Kjarri Sveinsso leaving to focus on his career as screen composer (his credits include the score to Neil Jordan's Ondine). Their first album as a three-piece, last year's Valtari, was muted and bleary, the work of a group trying to figure who they wanted to be, where they needed to go.
"It was weird," says Jónsi of Sveinsso's departure. "He provided us with tremendous support in terms of songwriting. Suddenly, we were a trio. We lacked that fourth dimension in the studio. We had to maybe try something different. There was a lot of experimenting."
If Valtari saw Sigur Rós tentatively searching for a new direction, with their seventh long player Kevikur they have assuredly found their way once again.
It opens with a crashing, quasi-metal riff and, from there, confidently cranks the melodrama. Jónsi explains that Valtari and Kveikur were written simultaneously, allowing the band explore flip sides of their personality.
"We were aware we had to shake it up," he says. "Our goal was an album that was moodier and darker. Maybe we wanted to return to basics, to the old days."
They haven't reverted completely to stereotype, though. For one thing ,they are considerably more outgoing. Two weeks, ago Sigur Rós performed on Late Night with Jimmy Fallon, the first TV performance in over 10 years.
And here is Jónsi, giving an old-fashioned interview (albeit following some gentle persuasion). You remind him of the way it used to be – of the handful of torturous press appearances Sigur Rós put in through the late 1990s, followed by a decade plus of silence – and he smiles.
"We have no idea why we did the TV show, really," he says. "We received the offer and were slap bang in the middle of an American tour. You think, why not? We have an album coming. Starting out, we were young and energetic and full of bravado. But we are older and don't care so much about whether or not we give interviews or do TV. You are young, you have all these principles. You think 'why are people talking to us – it's about the music'. And we had this outlook of, 'why are you taking our photographs?'. We hated that expectation to pose.
You get a little older and learn to take yourself less seriously."
Early on, Jónsi stopped reading his reviews. He was fed up with Sigur Rós being pigeonholed as 'glacial' or evocative of elves and fairies frolicking in the woods. Some insults bit deeper still.
"I remember an English magazine wrote a piece about one of our shows and said it was long and boring – that it sounded like Pink Floyd! I gave up on our press there and then."
As he says, back in the day, Sigur Rós were shy to the point that it almost came off as an affectation. Notoriously, in 2000, Radiohead, suddenly big enough to champion other musicians, invited the Icelandic group on the road.
It wasn't quite Mötley Crüe and Guns N' Roses going at it. The two camps were so wary of each other – of the world in general – they barely exchanged a word in their weeks in Europe. Reflecting on the time, Jónsi chuckles.
"It was like a competition between the two shyest bands in the world," he says. "It was awkward and funny. They were super nice guys and totally introverted. And we were introverted too. Pretty much nobody spoke to anybody. It was funny, with hindsight."
Jónsi feels he has grown grumpier and less precious with the years. There are undoubtedly signs of mid-life mellowing.
How unthinkable, for instance, that the Birgisson of 2000 would be caught waxing about the delights of David Guetta. He's a changed man. A po-faced avant-gardist who has learned to love the regular dude within.
"It's true, I like cheesy pop," he says. "There's nothing better than really good 'bad' music.
"I write a lot of that stuff on my own, on the road. It's harder than you'd imagine. You think 'oh, I'm in a cool rock band – I could make that dance music in a few hours. It's so easy'. Then you sit down and you try and, wow, it's difficult. Creating good pop music is a lot trickier than people imagine."
Kveikur is released today. Sigur Rós plays The O2, Dublin, in November.