Need a hit? A contract? Call David Foster. Almost every international pop star has knocked on his door for help. His songs have been on everyone's lips for decades and he hasn't been out of the hit parade for 30 years. He is the reclusive multimillionaire music mogul who fell for Elvis Presley's ex-girlfriend. Interview: Ariel Leve

Early one morning in sunny Malibu, a taxi turns left off the Pacific Coast Highway onto a private road. At the end, the trees part and electronic gates swing open. Along the winding drive, the driver rubbernecks in awe. "Does Michael Jackson live here?" he asks.

This is not Neverland — there are no llamas — but perched on the hill in front of us is a fairy-tale home. Villa Casablanca is set in 23 immaculately groomed acres and its owner, though not in hiding, rarely leaves. He takes few vacations, doesn't own other houses, and both lives and works here. "Where else would I need to go?" he says.

The taxi slowly rolls past a vast expanse of coiffed green lawn, a tennis court, a rose garden, and a cluster of beautiful women lazing on a marble stairway, waiting for a magazine's photographic crew to set up. Close by, a wooden sign points up a hill and says "main house".

It is the home of a superstar, not one whose face is recognisable or whose name could be considered household. But the owner is stellar in a galaxy of stars, a star-maker who has been consistently propelling people to the top of the entertainment industry for decades, a maker of legends and fortunes and fame. In the music industry, David Foster's name is revered.

He answers the front door himself. "Come on in," he calls out. "I'm just gonna hop in the shower!" At 54, he is well groomed, handsome, trim and boundlessly energetic. Today he will be bouncing from one project to another, dipping into business, creative and personal work with the agility of someone accustomed to making big decisions on the hoof. This morning is frantic, as usual. There are people — caterers, he thinks — milling about the front lawn, preparing for a charity benefit event he will be hosting with Mel Gibson. There is the photo shoot — a dozen people, aluminium cases of lights and camera equipment, and assistants who have assistants, setting up by the pool. And in one of the studios he has built, there is Celine Dion's latest album to be mixed.

Here at Villa Casablanca, Foster has six studios — and he needs them all, zipping from one project to another. In them he has fashioned, repaired or rejuvenated the careers of the biggest names in pop; composed, produced or arranged the scores of countless movie blockbusters. It is to Villa Casablanca that divas from Cher to Madonna will come to work. Barbra Streisand, Celine Dion, Whitney Houston and Natalie Cole have all made the journey to his door. Ghostbusters, The Bodyguard, Sleepless in Seattle, Moulin Rouge and, latterly, Troy are among the movies that bear his hallmark. He discovered the Corrs, Michael Bublé and Josh Groban. His shelves groan under the weight of 14 Grammy awards. His walls are covered with gold and platinum discs.

Racing from one studio to another aboard one of the many golf carts he needs to get around his estate, he confesses: "I used to feel that if I wasn't in the charts for six months, I'd slash my wrists."

David Foster has come a long way since Cat Stevens knocked on the door of his Earls Court bedsit in a purple velvet suit.Foster is tall, affable and boyish, with a thick head of greying hair. Back aboard the golf cart, we are on our way to the pool house to check on Renee Olstead, his latest discovery. Olstead, a 14-year-old singer from Texas, is a petite and delicate teenager with a voice that invokes the soul of Billie Holiday. Today, Vanity Fair is photographing her, and it soon becomes clear that when Foster takes on a project, he is the consummate producer — involved in the minutiae of the performer's image and overseeing not only the music, but also the image and the business.

Dressed casually in jeans and a rumpled, white, long-sleeved Oxford shirt, he strides quickly and delivers succinct instructions.

"I wish I had done this earlier," he says. "Being a guiding light or a guru or whatever. Or just a guy on whose tombstone it could say: ÔHe was good at finding new talent.' You know? It's very gratifying."

Finding talent is his third incarnation. Foster's career as a musician, songwriter, producer and the Midas of music has spanned over 30 years. First, in the 1970s, he wrote hits for Earth, Wind and Fire, and was a sought-after keyboard player and session musician, playing alongside John Lennon, Diana Ross, George Harrison and Rod Stewart. Then, in the 1980s and 90s, he moved into producing and writing No 1 singles, blockbuster albums and movie scores. But, by choice, he is now working less with the superstars and is instead discovering and nurturing new talent. His first album with Bublé sold 20m.

He sums up his work with the superstar divas such as Whitney Houston as "maintenance". This is recognition that he did not discover her talent, only galvanised it.

"You could arguably say, yes, I gave Whitney her biggest hit with The Bodyguard — but Whitney, during that time, was going to have a hit with or without me. It might not have been as big, but yeah, it's maintenance."

He is close friends with Barbra and Celine but admits he was never that close to Whitney, who has since seen her career crash due to drug abuse. "As much as I love her as a talent, to anybody that abuses the privilege, I say, 'Move over.' Because there are 10 others wanting to take your spot."

This no-nonsense attitude applies to his new talent too. Those who he agrees to work with enter his "camp" — which means that they must follow his rules, adhere to his guidance. He says there's no reason for him to work with someone who doesn't take it seriously; he doesn't need another hit record. He knows the value of image, and won't shy away from directing a protégé to lose weight. For an artist to have a career, he says, it's about staying the course. Longevity. There must be commitment and devotion.

Foster combines commercial savvy with his musical instincts. The music industry, he says, is about slots and knowing which slots need to be filled. Not only can he identify them, but he knows how to fill them and with whom.

"Right now, the Neil Diamond slot is wide open. For some young, guitar-slinging kid who plays three-chord music that everybody can relate to. You know what other slot's available? The Michael Bolton/Bryan Adams slot."

Now it's Renee Olstead's turn. Her slot has never been filled. "There's no traffic," he says. "There's nobody in her lane." Lately he has been coaching Olstead to eat properly and to get enough sleep. He told her she's going into battle. "She looks great, don't you think?"

Foster describes her as "a real purist" and, as she gets her hair and make-up done and tries on designer dresses giddy with the excitement of dressing up, he says: "I believe that she can be a role model for kids — like the Britney Spears spot in the beginning." But he admits that a sophisticated, mature voice from a 14-year-old might be difficult to market and that he's not sure yet who her audience may be.

We sit down at one of the shaded tables, and though Foster seems relaxed, he rests on the edge of the chair — poised to jump up at a moment's notice. Does part of him miss being the musician on the road, the star on the stage?

"No — I have the perfect life. I can get a great table at a restaurant and I don't get hassled when I walk down the street." He lowers his voice, punctuating it with displeasure. "Imagine, 24 hours a day, people coming up to you saying they have to talk to you — and it's the greatest moment for them, but it's an absolute zero to you, but of course you have to be gracious...

"I see it with Cher. She uses my studio a lot because she lives around the corner and we're friends. I used to be in Sonny's band in the 1970s, and she did her Believe album here. But when she shows up, everyone is whispering and talking. It's every waking moment of her life."

He waves his arm around to indicate the good life. "I know what my job is. I know what my slot is in the whole scheme." Just then he voices concern. "I don't sound like an egomaniac, do I? The printed word doesn't convey tone."

No. His tone hovers somewhere between someone who is used to success and has lived with it for so long they don't know anything else — and someone who has earned it, doesn't take it for granted and is afraid it can all go away if there's too much idle time. It is the tone of someone who is rich beyond even his superstar clients' wildest dreams, yet knows what it's like to be penniless and alone in a wintry London flat.

David Foster grew up on Vancouver Island, Canada, and had a "lower-than-blue-collar" working-class background. Nevertheless, he was classically trained and was awarded music scholarships, but he left school at 16 to move to England where he and his band played with Chuck Berry.

"I was poor as shit. When the Chuck Berry thing ended, the group went back to Victoria but I said, 'No, I'm not going home. I haven't made it yet.' By now he was 17. He stayed in England for another year, auditioned for children's shows playing the piano — anything — but he couldn't find work.

"London was just the wrong town for me. I sat in my little flat in Earls Court for a year and I had no money. I'm not crying about it, it was character-building — but the only money I had was spent on eating a Wimpy burger every day."

He had a little piano in his apartment and practised all day because he didn't know anybody. "Friends? Not one. Not one." He pauses. "I know it's sad. But the ending is great!

"Finally, after a year of this, I called my parents. I hadn't asked for any money at all and I'd lived off my savings from working with Chuck Berry. I'd rationed them out for a year. So I called my parents and said,'I gotta come home. Please send me a ticket. I'm so homesick, I can't stand it any longer.' They sent $60, which was what it cost to fly back.

"My plane left at 7am, and the night before, at 7pm, there was a knock on my door. I opened the door and this beautiful man was standing there in a purple crushed-velvet suit. And he said, 'Are you David Foster?' And I looked behind him and there was a purple Rolls-Royce. 'I'm looking for a keyboard player for my band to do a world tour.' It was Cat Stevens."

They sat down and started jamming. Foster played; Stevens sang — and at 4am, Stevens announced that he wanted to hire Foster. "I said, 'Mr Stevens, this is the greatest opportunity I've ever had, but I can't stay in this city for one more minute. I've got to go home.'" Foster went. Three months later his father died and he was thankful that he had chosen to leave.

But even at 17, Foster had the self- confidence to know that Stevens's offer wouldn't be his only chance. In Canada, he tried to finish high school but didn't. Music took over. He met BJ, his first wife, married, moved to LA and was signed by Capitol records as part of the band Skylark. They had a hit record called Wildflower, which reached the US Top 10.

When Skylark broke up he played rehearsal piano for $5 an hour. "I didn't give a shit because I knew that one day I'd be making 10 bucks an hour." Foster tells his children: "There's great dignity in flipping burgers if you know that in a year from now you're going to own the store."

Foster and his wife stayed in Los Angeles and he eventually got a job playing for the stage production of The Rocky Horror Picture Show. From 1975 to 79 he worked as a studio musician, and he would watch the producers on the other side of the glass.

"I learnt as much from the bad ones as from the good ones. And I just knew I could do that."

By 1979 he was making a great deal of money playing keyboards. He'd play on advertising jingles during the day then stay up all night with Rod Stewart or George Harrison recording albums.

"It was great — no sleep, working all the time."

After a few years he decided he was ready to produce records. But the first album he worked on never got released. The second was for a group that never worked out. His third was a solo artist; that didn't work either. After two years he became discouraged and considered going back to the keyboards.And then came Earth, Wind and Fire. A friend of his had given a song Foster wrote — After the Love Has Gone — to Maurice White from the band. They went to the studio to meet White, and Foster's friend introduced him. He played the song on the piano for White, who said he wanted to record it. "My heart was pounding," Foster says. "I asked, 'When do you want to record it?' And he said, 'Tonight!'"

Thus began his relationship with Earth, Wind and Fire — he went on to co-write all the songs on their album I Am. His career was beginning to take off at last. Soon after, he began working with Alice Cooper and the rock band Chicago.

He begins drumming his fingers on the table.

"I honestly believe that I don't know more than anyone else. I think that you could pick a hit just as easily as me. All that a hit record is, is something everyone wants to love. I've written my share of hits but I've had my share of flops too."

The times he's surprised himself most were the first time he ever scored a movie, St Elmo's Fire, and putting Natalie Cole together with the voice of her dead father in 1991 on her album Unforgettable — technically, he says, a great challenge.

In a 30-year career he has had only two short periods when he was not in the charts. One came at the end of the 1980s, the other at the end of the 1990s. After the first, he came back in the early 1990s with Celine Dion and Natalie Cole. But then, when Britney Spears and the Backstreet Boys hit, he says: "I found myself chasing instead of leading. So I thought, 'Okay, I'm 50. I want to keep making records — what do I do? I'm going to go outside the box.'"

"Outside the box" meant finding and developing new talent: Groban, Bublé and Olstead. "Ultimately," he says, "it will be even more successful."

He's now vice-president at Warner Brothers. "What I love about myself is that I've been able to adapt in a young person's business. I feel

really good about that."

As Foster strides past the pool, he calls out to ask someone if William, a young classical pianist he's working with, is in the studio yet. There is a monorail from the pool to the main house but it isn't in use. The pool has a built-in bar with underwater stools. He says he hasn't been in it for a while. When asked how long he immediately responds: "Um, a year." He laughs.

Foster is an alpha male and a family man. He muses that maybe he works so often and so well with women because, "I have six sisters, five daughters and two ex-wives." He clears his throat. "I actually have another daughter who's 34 who just came into my life a couple years ago." As we pull up to a different recording studio, he tells me: "It's a long story which we probably don't need to get into." Then, calling out to the studio: "You ready for me to listen to that mix?"

For the next half-hour, Foster has his elbows resting against the mixing board, eyes closed, his nose buried into the speakers. He is listening to a new arrangement of Celine Dion singing John Lennon's Beautiful Boy. Again and again the chorus is played. Foster closes his eyes. The vocal washes over him. When the track stops he says, almost unconsciously: "There's a steel drum lick in the middle of the last chorus..."

Back on the cart again, we are on our way to meet William. He is filling the slot that's open for a young, good-looking guy who plays classical piano. In the studio, working with William, there is a disagreement. Foster is adamant that the violin should not rise high at the end of the track but William believes it should be different.

"I could have said, 'Hey, f*** you — I'm 54, you're 24. You know nothing, right?' But I said, 'Okay, show me what you'd like to hear; we'll play it from the top and see how it sounds.'

"Is that manipulation? I wouldn't call it that. Who's to say who's right? Am I right for saying it shouldn't go up? Opinions are like assholes — everyone has one, right? My opinion is just an opinion. But it's an experienced one. But, you know, I don't ever want to take away someone like William's creativity — or his ideas."Foster's wife, Linda, arrives at the studio holding three Starbucks mocha lattes. Linda Thompson, a former Miss Tennessee, was Elvis Presley's girlfriend for five years and lived with him during his prescription-pills downfall — from 1972 to 1977. She watched him self-destruct.

Linda Thompson has a nurturing and gentle Southern presence and appears to be frozen in time as a twenty-something rock chick. She is dressed in low-slung jeans and a white tank top bearing the slogan: "Hard to Get". Her tanned and toned belly is remarkably flat and she tosses her blonde hair back, explaining how embarrassed her son, Brandon, gets when she shows up at one of his gigs. Foster worked with Lisa Marie Presley a few years ago and Linda marvels at how time has passed. "It was very bizarre — to be in the studio and to hear Elvis's voice come through and to see Lisa Marie there and my husband working with her. Life is full of surprises."

They have been together for 18 years. They met at the Grammy awards; Linda was sitting with Lionel and Brenda Richie. From the stage Foster spotted her in her orange dress.

Linda has established herself as a songwriter in her own right. With her husband she wrote the lyrics for Whitney Houston's I Have Nothing, and has just written Miracle, the title track for Celine Dion's new album. She admits Foster can be hard to live with. "He can be temperamental. To work with him, he is fantastic; he exhibits a lot of patience. He handles people very well and I think sometimes, when you come home, you're just tired of being diplomatic. So, yes, I have found him to be difficult. But he is also brilliant and fun, and the bottom line is, when you bring it to his attention, he's fair."

She is philosophical when asked if he has a desire to be the star. "Well, if he sang, he would have a career in the limelight — like Billy Joel or Elton John — because he is phenomenally talented. But he doesn't sing and he doesn't write lyrics either. You can't have everything."

It is late afternoon and we are back at the pool area. Olstead's photo shoot is winding down. Her CD plays in the background, and the lush and sultry sophistication of her singing voice is especially striking in contrast with the innocent girlish voice that chirps "great!" in response to Foster's question about how it's going.

Foster must disappear soon to change for a charity event he is attending, but for now there is time for reflection. Given his definition of success — "when a person leaves the room you know they're gone" — does he himself feel successful?

He demurs. "No." He explains that his reference point is the buzz that someone, a Barbra Streisand, or a Madonna, or a Bill Clinton, creates just by being in a room. There is a vague sense that this is still what's missing for him.

"People like Bill Gates inspire me." People who have had, as he puts it, a lightbulb moment. And his lightbulb moment? Natalie Cole singing with her father on Unforgettable?

"No, that's just a record."

There was a moment, Foster says, back when he was doing The Rocky Horror Picture Show, trying to be a studio musician and wondering if he was good enough, when he was sitting in his tiny apartment and he got a phone call. It was George Harrison calling to ask him to play with him in the studio. This moment, he says, was the moment he felt he had made it.

Now he's that phone call for the legendary divas or newcomers bursting with talent, who await an invitation to share studio time at Villa Casablanca. Yet Foster still seems to be waiting for something, perhaps for his phone to ring again as it did 20 years ago.

David Foster is again tapping his fingers on the table top. Even when he is still, he is in motion. His eyes widen as we discuss the lightbulb moment. "Maybe it's still ahead of me," he suggests. "Wouldn't that be nice?"