William Orbit greets me in the studio of his central London home and immediately apologises for being a little “tired and wired”. If I had caught him at nine in the morning, before he had gone to bed, he would have been in a much sunnier mood, he explains.

It’s not just an ordinary studio and not just an ordinary home. Orbit’s workplace is in the basement of his splendidly appointed Georgian house, just a few doors away from the home, as of next week, of the former prime minister. You get the feeling that the dormant rock star in Tony Blair would enjoy dropping in for coffee. The studio is a formidable sonic playground: eight keyboards, five computer screens, a Fender bass propped up in the corner. Stacks of amplifiers line the walls. Many of them are redundant, Orbit tells me almost nostalgically, replaced in function by tiny computer chips. He fusses considerately over my tape recorder, for fear that it will not pick up his quiet voice, but informs me we are in an acoustically controlled environment that would be hard to improve.

You had better believe it. Sound is William Orbit’s special talent. You would recognise his sound, even if you didn’t know it was his. Orbit was a pioneer in the early 1990s of the ambient electronic soundtracks that continue to accompany every sunset in every beach bar in Europe. His skills as a record producer are undisputed and much sought after, responsible for reviving the flagging career of the world’s biggest rock star when he worked with Madonna (right) on Ray of Light, and embellishing the music of Blur, U2 and other pop superstars.

It is not the twiddling of knobs and manoeuvres at the mixing desk that are keeping him up all night these days. Orbit has entered the entirely different sonic universe of the full, 100-piece classical orchestra and is putting the finishing touches to a freshly commissioned suite that is to be performed at the Manchester International Festival next month.

It is, he agrees with me, a task that is both scary and exciting. “I started it with a real moment of hubris – I thought: ‘this is easy, I must do it more often.’ And then about two months in, it suddenly became a very challenging and strenuous thing.”

But once he was in, he was determined to remain faithful to the spirit of the commission and not fall back on his area of expertise. “If it was going to be an orchestral suite, why sully it with electronic music? I didn’t even want to see a mixing desk. I wanted this to come from the heart of the musicians.”

Orbit had never worked with an orchestra before so one of his first tasks was to attend as many orchestral concerts as he could, “getting cheap tickets at the Proms, in the armpit of the orchestra, under the tubas, understanding the mechanics of it. And I found it so gripping, that’s when I made the conscious decision not to use electronics.”

Learning orchestra mechanics was one thing; the art of composing was another entirely. It was a steep learning curve, or, as he calls it, “a learning cliff”. He had to stop going to classical concerts, for a start, cowed by the intimidating mastery of classical music’s greatest composers. “It was depressing me. I wouldn’t have been able to carry on working.” With just a couple of weeks to go before the work’s premiere, he still worries with disarming frankness that his limits as a composer will be exposed. “I do shudder. Everything will be revealed: there is no hiding place. With pop production, there is so much you can do to obfuscate, but you can’t with this. I’m putting my soul into it, but sometimes I listen back and I’m thinking: ‘Is my soul really that shallow?’”

The more he has worked with the “brilliant” musicians of the BBC Philharmonic, he says, the more he has realised how much there is to learn. Sitting right in front of the strings made him understand: “That is where the pulse of the rhythm comes from. It doesn’t come from percussion like it does in pop music. It is there, in the heart of the orchestra.”

Was that an epiphany? I ask.

“An epi-phony,” he puns instantly. “Let’s coin a new word right now: an epiphony, a moment of sonic truth.”

At 50, Orbit gives every impression that sonic truth, rather than the continuation of a lucrative and much- garlanded career as a pop maestro, is what motivates him now. He reveals that he is shortly moving out of his luxurious home and back to his east London roots, not to escape from the new neighbours, but out of a wish to downsize. “To be debt-free,” he explains. “Music is a compulsion and I don’t want to be doing certain types of work just to pay the rent.” His next project is an opera, for which he has been told, by those who know, that he needs at least 2½ years.

It sounds as if the Manchester commission has been a life-changing experience, I say.

“Yes. But I know that doesn’t read well. I keep telling Alex [Poots, the festival director] that this marks a sea change in my personal development. But I think he thinks I am just being nice.”

I say he is brave, taking on such a tough commission. “There’s no bravery involved.” How about the critics? “I am ready for them. But I am going on holiday straight afterwards,” he jokes. “It’s fair enough. When established classical performers at the top of their field go into pop or electronic music and stumble, we are the first to tell them.”

Orbit has also just completed an album of new electronic music that he says contains some of his best ever material but he admits that he doesn’t quite know what to do with it.

“It’s not like the record companies are beating a path to my door for my next electronic record. They are beating a path to my door to produce pop singles. It is ironic.”

He emphasises that he still loves electronic music, finding more similarities than dissimilarities with the orchestral sound universe in which he has immersed himself.

“I have never been very good at marketing myself,” he says candidly. But he has worked with the best self-promoter in the universe. “I know who you mean. I don’t want to talk about her. But someone like Tracey Emin – she is so brilliant at it, whatever you think of her stuff.”

I say he should get her to do the set designs of his opera. He doesn’t rule it out. “I’m moving to Hoxton. Or Hoxtonia,” he says almost guiltily. “Right next to White Cube. I like it, it is where I came from, and it feels vibey.”

But for now, the stately world of the orchestra awaits. He has heard that tickets are being snapped up by under-20s and over-60s. “That is marvellous. And I can guarantee,” he says with rare bullishness, “that anybody who comes won’t regret it.”

‘Orchestral Suite’ by William Orbit is at Bridgewater Hall, Manchester, on July 8. Manchester International Festival opens on June 28; for full programme details, see www.manchesterinternationalfestival.com