“I actually don’t like soundtracks,” says Sufjan Stevens. “But it’s unavoidable – there’s music accompanying us in shopping malls, airports, in our cars, on the TV. There’s a part of me that really loathes music’s omnipresence.” He pauses. “But at the same time, music is constantly in my head.”

Stevens doesn’t pause much, so there’s a temptation to regard every one as meaningful. It’s wiser to pay attention to what he’s saying. Those used to his singing voice, diffident yet affecting, might be surprised by his talent for monologuing like a dorm-room philosopher. But Sufjan Stevens lives to surprise.

He set the world on fire with Illinois – part two in his “Fifty States Project”, a plan to record a concept album for every state of the union – and acted like it was no big deal. He has produced an album of electronica based on the Chinese zodiac, five EPs of Christmas songs, choral folk, orchestral arrangements and has an upcoming set of improvised instrumentals designed “to evoke insomnia”. Last year – one of his busiest ever – after scoring Natalie Portman’s 22-minute directorial debut Eve, he said he was unlikely to write any more film soundtracks, with exceptions made should Cassavetes, Antonioni or Kieslowski return from the dead.

Despite such sentiments, Stevens now offers his fascinated fanbase The BQE, a multi-headed animal comprising a film, an original score, essays, photography and a comic book, all inspired by the Brooklyn-Queens Expressway, a subject which seems unlikely even for the man who rhapsodised Michigan. “I intended to create a non-personal, non-narrative piece. I tried to reduce my own personal investment as much as possible, and I refused to incorporate one of my strengths, which is the song. I was relinquishing my greatest weapon,” he chuckles.

The expressway itself is not looked upon with love by most New Yorkers; it’s notorious for congestion, noise, smog and depressing physical unattractiveness, and no-one knows it better than Stevens. “The music is an imposition,” he says. “It’s heightened and transcendent, and the BQE itself is not a very enlightened experience. It’s an ugly, monolithic source of traffic and pollution and the object of scorn. So I decided to go the other way and recreate the BQE as I would have imagined it, which is as an object of beauty and perpetual motion and reflections and lights and colours. But it’s a complete fabrication; the beautification of a monumental beast. I think that’s typical of me, so if there’s anything personal in the project, it’s that.”

In early 2007, the Brooklyn Academy of Music (better known by its Flintstones-esque acronym, BAM) approached Stevens with a loose brief: “The only stipulation was that it be 30 minutes long and about Brooklyn,” he remembers.

From there (unsurprisingly for Stevens), the project grew increasingly, confidently grandiose. A 16mm film was made, documenting New York from the BQE’s point of view. A band was assembled, and then an orchestra. A trio of hula hoop artistes was included and provided with costumed identities: the “Hooper Heroes”, who star in the vinyl edition’s accompanying comic book (written, of course, by Stevens). All of which came together for three successive nights of performance at BAM in November 2007, each night selling out the academy’s opera house without advertising. What was the experience like?

“Stressful. Reckless. Everything hanging by a thread. The video had to match up with the music, cued by a score-reader, triggered by a videographer, with a conductor keeping 30 musicians together. The music isn’t necessarily sophisticated or revolutionary, but it’s very ... athletic.”

An inescapable comparison for a piece such as The BQE is the work of Philip Glass, one which Stevens invites. “He’s definitely an unavoidable influence in all contemporary music. He plays a huge role in almost everything I write, since I listened to so much of that music as a kid. BQE makes pretty strong reference to Koyaanisqatsi, but the score is way more romantic than anything Glass has ever done. He’s very consistent in his ideology; his classroom hasn’t really changed in the past 30 years. That’s his thing, and he helped create it, so more power to him.”

After the “cinematic suite” was played to a mixture of classical music aficionados and soldiers of Sufjan, Stevens took to the stage in his trademark rainbow-coloured eagle-wings to play some of his better known numbers, including a deeply emotional rendition of John Wayne Gacy, Jr, his ballad about the Illinois-born mass murderer with a day job as a children’s clown. Entirely free of serial killer chic, it poignantly meditates on the best and worst that humanity is capable of, but afterwards Stevens suggested he no longer wished to play the song, since he no longer felt as he did when he wrote it. I inquire if this is still the case.

“Your relationship with your music changes pretty dramatically over time. That song is problematic because of the subject matter, and requires a certain psychological investment that isn’t always fruitful ... or healthy. At the time, I was fatigued, and just too despairing and existential to get through it. Now I feel a real healthy disassociation to my songs, and I no longer have to reconstruct the emotional climate at the moment of writing it in order to sing it. I played it on my last tour, and I never stumbled.”

Those who can sort the myths from the reality – a few years ago, Stevens was putting it about that he was abandoned on his parents’ doorstep in a milk crate – will know that Brooklyn is not Stevens’s first home. He was born in Detroit, and lived in Michigan until he was in his early twenties. Despite or maybe because of this, he feels a ­powerful connection to the city and its mythic undertones.

“New York was pretty abstract to me when I was growing up in Michigan; so foreign, so gargantuan. My first trip out was when I kind of quit college and moved to the city to see if I could make it – and it was a very tragic year for me. I went back home, finished college, but felt like I wanted to give it a second try. I felt galvanised. The character of New York seemed greater than all the characters within it. And if you’re going to exist and survive here, you had to learn to yield to that.”

I ask how he feels about Robert Moses, the city planner who designed the BQE itself and about whom every New Yorker seems to have strong opinions. “He was in a position of power in post-war America, when there was incredible federal funding for reshaping the cities, so he was able to transform on a massive scale – more than anyone before or after him. And now we’re living in the shadow of a building boom in New York, but it’s all private investors focused on capital, devoted to a very personal kind of corporate greed, so there’s been an interesting change of opinion about Moses. The people now long for a master plan.”

As with all his work, The BQE is being released in the US by Asthmatic Kitty, the record label he helps run with his former stepfather, Lowell Brams (and named for Sara, the cat Brams rescued, pregnant and starving, from the woods near his home, and which sadly passed away last December). How are they dealing with the latest recession?

“Our label’s suffering a lot, because people aren’t buying records any more. But at the same time, it’s teaching us to be much more resourceful and industrious. We’ll see how we fare. I’m invested in music and art, and I couldn’t care less about money. I know we’re a business, but we’re a business of artists. You have to keep your priorities straight.”

He takes one of those could-be-significant pauses. “Not enough people have drawn a relationship between our economies and the sustaining of resources – that kind of green revolution is inversely correlated to the recession. Not enough people are making comparisons between those two things, and celebrating the side-effects. Society cannot be maintained by eternal, infinite, exponential growth.” He sighs. “We’re only here for a short time.”

I ask if he feels like taking it easy in 2010 after the year he’s had. He perks back up. “Oh no. I want to do a lot more, actually.”

The BQE by Sufjan Stevens is released by Rough Trade