Beyoncé Knowles is nothing if not well-mannered. A flunky at the photographer's studio in midtown Manhattan where we meet approaches her brandishing a cooler containing a bottle of champagne. It's for her, he explains, from the management, just to say thanks for being here. That sort of thing happens a lot to her.
"Ah, that is so sweet," she sighs at the awestruck fellow, "but I'm not drinking right now." The subtext is clear: I am not drinking, ever. I have a new record to promote. And I don't particularly want anything to threaten my status as the world's leading pop star, least of all a hangover. She bats the gift over to the two stylists working on the shoot. It's a strangely unaffected moment. "They'll like it more," she says, a little apologetically, by way of explanation.
The 24-year-old singer is nothing if not controlled. She probably has to be to retain her position as the leading force in American R&B, pop's international currency of hits. Despite competition from the likes of Justin Timberlake and Christina Aguilera, she remains the music's biggest draw. Keeping that title means more than refusing champagne: it means sticking to a rigid career plan that leaves no margin for error. Promoting her forthcoming album, B'Day, for example, is just the latest stage in a plan drawn up two years ago. She takes work extremely seriously: despite her previously stated dislike of promotion ("If I can be honest with you, and I hope I can, I hate doing these things," she told one interviewer a couple of years ago, when he asked if she was bored), she will turn up at the launch parties for B'Day in New York, Paris and Tokyo, which wouldn't be so notable were the visits to the three continents not scheduled for just two days, September 4 and 5.
But the result of such intense professionalism is an ability to stay ahead of the game artistically, too. Even after a series of landmark singles, both solo and with the now-defunct Destiny's Child - from Bills, Bills, Bills to Crazy in Love - she is still in a league of precisely one when it comes to creating a peerlessly modern, tricksy groove and adding some possessed performance chops to the mix. You don't sell 50m albums by accident.
A few months back, BBC2 ran a documentary series about the history of black music, called Soul Deep. Some reviewers criticised it for dwelling on soul's 1960s golden age, and glossing over modern R&B. But a brief sequence towards the end of the series demonstrated that Beyoncé is more than just a pop star - and helped explain her dominance in the R&B market. With Destiny's Child, we were told, she had revolutionised singing in US urban music - with her distinctive, fast, almost hiccuping vocal technique, she had changed the nature of the music. She had taken it in a new direction, consciously or not.
But it took time for the music industry, and Knowles, to realise her talents. Beyoncé's recording career began in 1996 with a relative misfire, Destiny's Child's eponymous debut album. For a season, Destiny's Child looked like a poor man's TLC, with a little of the then-hip neo-soul trappings of Jill Scott and Angie Stone. "The first record was successful but not hugely successful," says Beyoncé. She understands the reason why. "It was a neo-soul record and we were 15 years old. It was way too mature for us."
Even then, though, the intense and overpowering ambition of Beyoncé and her family (she is managed by her father) was evident. An executive from her US label told Billboard earlier this year about an early piece of promo, at a show put on by a radio station in a small Virginia town.
"They were in a parking lot in front of a department store on a one-foot riser with a stage. Yet those girls came prepared like they were playing Madison Square Garden. They were doing their own hair and makeup, complete with costume changes. Tina [Beyoncé's mother] literally sewed all the clothes back then. There were no lights and cameras. Just them and a crowd of people. And they killed it."
Although the debut album spawned a major hit - Wyclef Jean's remix of No, No, No - it took until the follow-up, The Writing's on the Wall, for Destiny's Child to make their breakthrough, and for Beyoncé to find her voice. The conscious soul flim-flam of their debut was swiftly erased and, in its place, a clipped, polyrhythmic bounce buoyed the group's increasingly confident songwriting.
"That staccato, fast singing has kind of become the sound of R&B. It's still here in 2006," points out Beyoncé, correctly, "But we had no idea of what its impact would be. We had no idea that The Writing's on the Wall would be as big a record as it was. Especially worldwide. You have to remember at that time that we'd talk to people at the record company and they'd say, 'Look, they don't even play R&B in Europe right now.'"
The key to the breakthrough lay with one of the producers hired to work on the album, Rodney Jerkins. "The first time we worked with him we wrote Say My Name to a track that we didn't like," Beyoncé says. "I don't think he liked it either. There was just too much stuff going on in it. It just sounded like this ... jungle. I don't even know to this day how we wrote that song over that track.
"It wasn't going to make the album, and then when we were doing the photo shoot for the record my dad came in to the studio and said, 'Rodney's done a new mix of that song that you hate but you just have to take a listen to it.' He played the mix to us and we couldn't even focus on anything. He had turned it into an amazing, timeless R&B record. It was just excellent. It was one of the best songs we ever had, one of the best he's ever produced. It felt right from that moment on."
The Writing's on the Wall turned out to be a prescient title for the album. Destiny's began their golden run of peerless pop singles: Bills, Bills, Bills; Bug-A-Boo; Say My Name; Jumpin' Jumpin'; Independent Women; Bootylicious; Survivor. Beyoncé liked the taste of success - "Sure, it felt good" - and Jerkins entered a tenure as the hottest name in contemporary American soul production, farmed out to everyone from Michael Jackson to the Spice Girls to lend them some of that Destiny's pizazz.
Though a technical maestro, Jerkins says working with Destiny's was largely based on intuition. "It's just a feeling you get. That feeling ... you just know, 'We got it!' We write every day, but there are always those [projects] that stick out," he told Mix, an online music industry magazine in 2004. "You get excited and you're almost ready to celebrate on the spot because you know the potential. That's how it was with Destiny's Child."
There followed moments where Beyoncé, rarely one to rest on her laurels, would feel a penetrating sort of song-envy from sharing her production house with a string of artists waiting to be touched by Jerkins' production magic. The first time she heard Brandy and Monica's exquisitely refined duet The Boy Is Mine - in which Jerkins had magically fashioned a club banger out of a song set at the dancefloor-clearing slow pace of 85bpm - she was aghast. "How did he do that? I mean, how does he do those things? It's just magic."
Despite her perfectly composed public persona, she is not above jealousy. "Oh, absolutely. When I hear a great new record, especially when it's by someone that I respect and admire, then a part of me is like, 'Why didn't I think of that? Why didn't I write that record?' It makes you sick, but in a way it can be a great thing. It makes you want to go back to the lab and start writing again. Maybe it will inspire you to try a little harder."
As Destiny's set about becoming the world's bestselling female act ever, it became clear who the star was. Industry rumbles hinted at a Supremes dynamic emerging, with Beyoncé as the Diana Ross of the equation. The line-up changes of the early years (it took three albums for the group to arrive at its familiar trio, completed by Michelle Williams and Kelly Rowlands) led to the former members suing Matthew Knowles, his daughter and Rowlands for breach of partnership. The cases were settled in July 2002.
She rejects the Supremes comparison firmly. "The reason is because I loved being in a group. I do love sisterhood. I loved that being in a group was about compromise and sacrifice. All of us - and not just me, this is about Kelly and Michelle also - whatever was best for the group, no matter whether it was best for us individually, would let something go. That element of compromise and sacrifice taught me a lot about myself and about friendship."
But Beyoncé forged ahead regardless, as she gained knowledge from producers and branched out into a solo career that initially ran alongside her group activities. In summer 2003, her personal stardom eclipsed that of her group with the release of Crazy in Love, featuring her boyfriend, Jay-Z, rapping. You would think creating a single that fantastic would be a cause for pride, but she has already moved on: "I took a chance. It worked," she says, before making it clear that making a record that everyone loved one summer is not all she wants. "I'm not interested in the moment. I'm interested in how this is going to sound in 30 years' time."
But she learned, too, from Jay-Z, how to make herself more than just a pop singer. "He has taught me about hip-hop. I loved it as a child, but my mom wouldn't let me listen to the cussing. Now I understand it. It is a reality." And the couple - are they the Clinton administration of urban music? "I'll take that. It sounds good."
At that level of fame, however, the dangers are enormous. We speak a little about the incumbent problems that American stars seem to fall prey to as they straddle her level of success. We talk about Mariah Carey's breakdown, Mary J Blige's beaten drug habit and Whitney Houston's ongoing one. She adds Michael Jackson into the pot. "Do I worry about that?" she says, softly "No." There is a pause. "I mean, I just cannot worry about that."
I remind her that the last female soul singer to threaten the kind of global pre-eminence Beyoncé is aspiring to, Lauryn Hill, ended up shaving her head and touring Brooklyn high schools to sing folk songs with an acoustic guitar, sabotaging a brilliant nascent career.
"Her story is the most tragic," she agrees. "I mean, her record was genius. But the drama and the demands and the pressure and all of the people giving you so much access to so many things can be too much. So couple that with everyone telling you you're so this and so that and so perfect and of course you can lose yourself.
"The thing that I always say is that I'm lucky to have my family around me. But it's true. I'm really not worried about that. I don't know what's going to happen. I'm 24 years old. I would be dumb to say what I'm never going to do. I'm too young and sure I'll change a hundred times over my life."
She seems a very different woman now to the Beyoncé of five years ago. "Oh, absolutely I am. But I feel like the older I get, the more I'm not worried about having a breakdown. I don't know what's going to happen to me but I know that I'm more than a singer and I have so many other things in my life to keep me focused. I hope and pray that I stay as comfortable in my own skin as I am right now, at this exact moment."
She may have found her saviour yet. I ask if work is her drug. "It is. It is. If I had a drug? Uh-huh, that's it."
· B'Day is released on September 4 by Sony/BMG. To buy a copy for £12.99, call the Guardian music service on 0870 836 0712
A selection of Beyoncé's most bootylicious singles
(In order of release date)
1) Crazy In Love (featuring Jay-Z), 2003
Dispensing with traditional verse/chorus/verse construction, this goes for pure danceability. Beyoncé's rich vocals are offset perfectly by Jay-Z's blistering guest rap, in which he rhymes "Jay-Z in the range" with "crazy and deranged".
2) Baby Boy (featuring Sean Paul), 2003
Beyoncé collaborates with Sean Paul on this single, in a track that bridges the gap between the genres of R&B and dancehall. Yet the chemistry doesn't live up to the sparks produced whenever Beyoncé and Jay-Z get together.
3) Lose My Breath, 2004
As if we needed any more proof after Survivor, this track further relegated the other members of Destiny's Child to the position of Beyoncé's backing singers. Claims of "more equality" amounted to Beyoncé not appearing in the middle of the photo on the album cover.
4) Check On It, 2006
The first single from B'Day once again espouses a blissful disregard for traditional songwriting conventions. No Hova (Jay-Z) this time, but Houston rapper Slim Thug's lazy southern drawl suits the fractionally slower tempo.
5) Déjà vu, 2006
The new single does for basslines what Crazy In Love did for horn samples. Jay-Z faxes in an average performance by his lofty standards, but B is her usual brassy and soulful self. With a sexy video in tow, the smart money is on another huge hit.
By James Anthony