We snake our way through the backstage village of Portakabins that house the support acts for U2 at Slane. Glancing round, we see Rick McMurray, Ash's Mohican-haired drummer, lounging about and Louis Walsh, the pop supremo, high-fiving with Denis Desmond of MCD, the concert's promoter. It becomes apparent that we're here because of a confluence of ironies, "clerical errors" and, perhaps, luck.

The object of our visit is a small bald man who wears faux National Health Service prescription spectacles, a Black Flag T-shirt and ripped-at-the-knees jeans. Analytical and a self-confessed intellectual dilettante - he says that he can pretend to be smart about anything, but also that he knows a lot about only a very few things - the 35-year-old is probably the most surprising pop-music success of the past five years.

Three years ago, Moby was a peripheral figure. Ten years ago, he was Richard Hall, a former philosophy student at the University of Connecticut who relocated to the State University of New York.

Musical training in his teens consisted of learning jazz fusion and classical guitar from a member of a heavy-metal band, while his roots in punk rock caused initial consternation among the techno fraternity (at a 1993 dance-magazine event at the Royal Albert Hall, in London, Moby, by then a minor star through Go, his 1991 hit single, trashed his equipment).

In 1995 Everything Is Wrong, his debut album, fused punk and house to dramatic effect, effortlessly seducing the dance contingent. The follow-up, Animal Rights, from 1996, was an about-face, a hard-core noise/punk album that, wilfully or not, disenfranchised his small following.

"I made a record I liked," he says, "and that other people didn't." In a roundabout manner, this brings us to Play, a collection of tracks that started out as another record Moby liked. Released in the summer of 1999 to a subdued, almost wary public - the memory of Animal Rights was difficult to shake off - it has sold in the region of eight million copies, with the Republic topping the per-capita sales table. Its success has made Moby more than a fringe artist. And, even at a paltry dollar for each album sold, Moby can no longer be described as struggling.

But the success of Play finds him at a crossroads. Like Animal Rights, it was created "organically" in his two-bedroom apartment in New York. Animal Rights, he claims, is as much a part of his musical CV as Play. "If Play had failed," he says, "I guess I would have felt I was destined to be a marginal figure, like most of my heroes."

It never happened, of course. While the album's mixture of acoustic piano figures, raw blues field recordings and ambient sound treatments hit a cosseted nerve with the in-car-entertainment crowd, the coffee-table set and the chill-out brigade, its cross-generational appeal can be pinpointed in two things. First, it is a record of emotional depth. Second, it is the first pop album to have all of its tracks licensed for advertisements - at least 500 at the last count.

"I wasn't really aware of it," says Moby, pricking up his ears as U2 bang their way into Elevation. "The ubiquity of Play wasn't near as much in America, where I live, as it was in the UK and Europe. I was flattered by it, if anything. Ultimately, I make music and I want people to hear it."

All of which begs the question of what Moby will do next. He is mixing his new, as-yet-untitled album, due out next summer, so will he play the game and release Play II, thereby ensuring his place in the queue for the pop premiership's executive toilets, or do what Radiohead have done, and release a record that will alienate his new-found aprΦs-dinner-party fan base?

"The logical step would be for me to try to make the coolest, most cutting-edge, high-tech avant-garde record in the world," he says. "What I actually think I'm going to do is to make a nice record. All I've ever wanted to do is to make a nice record. I never wanted to be, or aspired to be, innovative. I don't think I have ever been particularly innovative. I just want to make music that I like. So the follow-up to Play is going to be a little more song-oriented, and not experimental or avant-garde. I don't want it to be ground-breaking, I want it to be a record that someone can listen to from start to finish, and for it to be a profoundly satisfying experience. That's my ultimate goal."

He says that when Play went to No. 1 for the first time, he thought it was a mistake, a clerical error. People, he smiles, picking at a frayed thread in his jeans, had clearly bought the wrong record from the right shop, and the next day would return Play in exchange for something else.

"I look at the pop climate and I don't understand why Play was so successful, because it's such a weird record. It's diverse and eclectic and it doesn't really fit in anywhere. But I've finally accepted the fact that Play was, is, a genuinely successful album."

Moby says that, money and profile aside, not many things have changed since Play was released. Living in the midst of New York's boho SoHo scene brings its own level of celebrity, with its reputation for hedonism and debauchery and a guest list that includes the likes of Winona Ryder, Elton John, Natalie Portman, David Bowie, Madonna, Bono, Beck and Gwyneth Paltrow. As a vegan and a Christian, Moby is a rock star who lacks the ego for self-absorption. Celebrity parties? He does everything to avoid them.

"The night before Slane I was back in my hotel room by midnight, reading a book, thinking: this is such pathetic rock-star behaviour," he admits. "I could have been getting drunk and flirting with models. Degeneracy and debauchery can be fun, but I feel I've been to enough average celeb parties to last me a lifetime. It's fun when they're completely over the top, the one big blow-out.

"If I tried to live the M÷tley Crⁿe lifestyle, constitutionally I couldn't do it, I'd probably die. Of course, they're trying to fill a void, but the truth is I've never woken up sober and wished I'd gone out the previous night, had too much to drink and had bad sex with a stranger.

"The interesting thing about hedonism is that it and the lead-up to it seem so compelling, but afterwards they seem so shallow and empty. There's nothing wrong with that, except the cumulative effect of lots of it is brain damage and heart failure. It can be fun, but what's the point of having fun if the only legacy is going to be bad health?"

Musicians aren't on stage for themselves, they're there for the audience, says Moby. He likes performing anything, and says he has never become sick of a song, which is good news for fair-weather lovers of Play and bad news for those who believe Animal Rights was a creative shot in the foot.

By Moby's definition, a live performance is a service industry. He's such a populist, he says, he feels that if he can make people happy by playing songs they want to hear, then why not play them?

A curious mixture of inner-sanctum gatecrasher and seemingly asexual pop-star aesthete, Moby has an agenda that appears to be distinctly idiosyncratic and watchful of deceit. "I hate the idea of anyone suffering needlessly," he says. "I aspire to live by the teachings of Christ to an extent - forgiveness, compassion, love, humility - which is obviously quite difficult."

How admirable - but what's this? He drags his hand over his head, producing a smirk and a punchline. "I still like to get drunk now and again, however, and will probably do so for the rest of my life."