Mark Ronson emerges, cradling an alien copper-coloured box with protruding wires. It's a Theremin-style synthesiser, he tells me, a belated wedding gift from a friend, the XL Recordings boss Richard Russell, for when Ronson married the French actress and singer Josephine de la Baume, in Aix en Provence in September.
"I think it's one of those wedding presents that's probably more for me than for me and my wife to enjoy together," he says. "But she got a couple of those, too, like: 'Hey, congratulations on your wedding. Here's a handbag!' We have joint custody of the handbags."
The gift is coming in use for Carbon Life, the ballet that he is creating alongside choreographer Wayne McGregor, and which is to be premiered at the Royal Opera House on 5 April. McGregor has asked him to "design some different sounds and make a bunch of noise between songs," and the synth will be perfect for the job, says Ronson, tall and smart in plaid shirt, and youthful-looking for his 36 years.
The project came about two years ago, when McGregor contacted Ronson and asked him to take charge of the music. It's a different project to those which Ronson usually takes on as a Grammy-winning producer, most famous for Amy Winehouse's 2006 album Back to Black, the hotly anticipated upcoming albums from Rufus Wainwright, and Ronson's own Top 5-charting solo albums, including the triple-platinum covers album Version. But the musician didn't think twice about taking on the new challenge.
"I didn't really have to think about it because it was the prestige of the Royal Opera House mixed with just knowing what a don Wayne is in his world – he's the most sought after choreographer in the world."
With his ballet experience limited to traditional classics such as The Nutcracker, Ronson set about watching another of McGregor's contemporary works melding pop with dance, Chroma, for which the choreographer took orchestral arrangements of songs by Jack White of The White Stripes. But it was when he was taken on a tour of the Opera House to see some modern dance rehearsals in action that he was unexpectedly moved by the artform.
"I'd never really watched any modern dance and there was something about the ultra-jagged movements of this girl that was dancing; it was almost like an Edward Gorey flip-book or something. Just the way the movement was, and I don't know why but I just started crying in this rehearsal room. It was super-powerful, and I didn't really think too long before I agreed to do it." The first thing that struck him as posing a difficulty wasn't the project itself, but the long time-frame involved.
"Obviously it was like two years in advance. When you work in things like the ballet and opera, that's nothing, but for me – for musicians – two years is like dog years. He [McGregor] might as well have said 2020." What does he think made McGregor ask him?
"He'd been to a few of our shows and he liked the way we had different artists walking on and off stage. And I guess the music, and, especially for him, the rhythmic factor in it, because his dance stuff was [characterised by] jagged movement of the bodies. Maybe there was something about the stuff rhythmically that struck a chord with him."
Later, McGregor tells me: "I love that his work is so eclectic and that he is totally collaborative. Mark's music is brilliant for dance because it not only has rhythmic drive but it suggests fantastic atmospheres in which I can easily imagine bodies moving." Ronson teamed up with songwriter Andrew Wyatt, lead member of indie pop act Miike Snow, to write nine songs for the show, and together they picked Alison Mosshart of The Kills, Jonny Pierce of The Drums, Boy George and rapper Wale to sing and take care of the lyrics. Ronson employed his friend Rufus Wainwright to score three of the orchestral arrangements.
As Ronson and his band The Business International combine with the orchestra, dancers from the Royal Ballet will be performing in costumes designed by Gareth Pugh, surrounding the guest singers.
The overarching theme is love, sparked by the Jung writings that Wyatt was reading at the time. Ronson rattles off a potted explanation: the archetype, the animus and the anima, the different stages that you go through in your own sexual development; sexuality and finding love. "I had to have Andrew explain it to me. I got the crash course," Ronson says. They played around with those concepts, and each of the singers gave their own perspective on love.
"Some of Alison's pieces are these wild, unruly passion, love letters put into song and some of Jonny's lyrics look at how love can be this incredibly pure thing that's just an extension of nature. And Wale talks in a more contemporary sense of how sometimes you're just trying to get a girl home and all the things you say, all the bullshit you'll spout, to try and accomplish that. I guess you ask one person about love, and everyone has their own articulation of it. It's almost like the whole thing is a split personality."
Making his first foray into ballet is not the only challenge for Ronson this year, which will see the release of the anthem he has created with Katy B, one of Britain's biggest dance-pop talents, for London 2012, fusing the sounds of Olympic athletes to music. After many years spent living in New York, the British-born Ronson has returned to his roots, and is now living in London's Ladbroke Grove.
But first, a stint in one of the UK's most prestigious venues. Tickets for the ballet start at just £3 and are capped at a reasonable £42, a fraction of the prices commanded by the Royal Opera House's biggest shows, in a move to draw a younger crowd. "Wayne's very passionate about getting a different audience into it," says Ronson, who recalls seeing Monkey, the Damon Albarn and Jamie Hewlett opera, at the prestigious venue. "It was exciting to go into that kind of building and look around and see the same crowd that you might see at Heaven on a Saturday night at the Opera House, so hopefully we can get some of those people in."
Later I join Ronson as he makes his way to a rehearsal in Islington with his band members, The Business International. He takes the role of musical director, sitting round with the musicians as they pore over the scores and work out how to adapt their own parts alongside the orchestral arrangements. From the hip-hop of Wale's track to the urgent, impassioned vocals of Mosshart, all set to a swirling orchestral score, it sounds musically exciting and unlike anything staged there before.
"Part of the pressure was coming up with some good material, but then we also have to perform it on the night. So I feel like we're halfway there, but then we're playing in a building live, with an orchestra that's not used to having a full band, and then you have singers performing onstage with the ballet going on around them," says Ronson. "We're going to have to rehearse this to death to make sure it goes off without a hitch." He adds seriously: "Listen, if we're on stage at the Forum or something and something goes out, that's kind of all right... but you can't do that at the Royal Opera House."
'Carbon Life', Royal Opera House, London WC2 (roh.org.uk) 5, 10, 12, 14, 18 and 23 April at 7.30pm