If you were trying to create the perfect 21st-century soul man, it would be difficult to come up with someone better than John Legend. The Ohio-born, Philadelphia-educated, New York-resident singer, songwriter, producer and label-owner deftly balances emotion with reason, inspiration with hard work, and talent with the level-headed sense to know how to make the most of it. In an era when having a good song and a decent voice is only part of what it takes to succeed, Legend is the complete package. In his mind, though, the only surprise is that more people don't follow in his footsteps.
"The hard work has been worth it," Legend says, eyes bloodshot after an overnight flight to Britain. "But my hard work is being in the studio and doing shows. Yes, there's interviews and promotion, but a lot of it is just doing what I love to do anyway. So it's work, and it can be tiring sometimes, but all work is fun. I'm lucky."
According to the cliche, people make their own luck. But even allowing for his work ethic, Legend has enjoyed some good fortune. Born John Stephens in December 1978, he was given his nickname at university. A childhood love of the piano became a career in the late 1990s, when a friend recommended him for piano work on the track Everything Is Everything, which appeared on the multi-million-selling debut LP by the Fugees singer and rapper, Lauryn Hill.
Legend then moved to New York, built a reputation as a formidable session player and released a series of self-financed CDs, before coming to the attention of another cerebral hip-hop artist, Kanye West. West took Legend under his wing, gave him vocal and instrumental spots on West's LP The College Dropout, then signed him to his label. West also oversaw production of Legend's debut proper, Get Lifted. The album was released in December 2004 and became a huge global hit, winning three Grammys in 2006.
One Grammy was for the song Ordinary People, which has achieved the ultimate in widespread, sublime-to-ridiculous approval. Everyone from Paul McCartney to Stevie Wonder has told Legend how fine a piece of songwriting they think it is, yet with its accessible register and deceptive simplicity, it has also become a staple of American Idol auditions. "It's right in that sweet spot of songs that everybody thinks they can sing, so they all try," he laughs. "But it doesn't matter to me if it's bad - it's flattering every time."
Perhaps part of the reason Legend has succeeded where others failed is that he never over-complicates his music. Nor, despite the patronage of hip-hop's A-list, is his sound a rough-edged rap update of the gospel-inflected soul music he grew up with. Rather, he is one of a select band of artists trying to return soul to its 1960s and 1970s essence not by slavishly recreating the sound of a bygone era, but by analysing what that music meant and how it functioned in its own time, then bringing those feelings into a contemporary setting. On his second album, Once Again, released last year, Legend seems to have succeeded even more emphatically in grafting soulful authenticity on to a sound definably his own.
"My references for soul music, in the classic definition, are people like Aretha Franklin and Curtis Mayfield and Al Green," Legend says. "People who made music that had a certain grit to it, that had an authenticity to it, a root in gospel and blues. But I kinda know what soul isn't as well: it's not over-produced, it isn't too slick, it doesn't sound contrived. It sounds like you were pouring your heart out on the record.
"There's a difference between soul music and soulful music," he continues. "Jeff Buckley, Mick Jagger, Fiona Apple, Arcade Fire - all kinds of people make soulful music without exactly making soul music. I make soul music, but I also try to make soulful music, and I like listening to other people who make soulful music, too."
The soul greats Legend looks up to - the Marvins, Stevies, Smokeys and Slys - were around in an era when soul music dominated the pop mainstream.
"Making soul music pop again has actually been my mission," he says with a quick chuckle. "That's what this album [Once Again] was an attempt at. It wasn't like, 'I gotta be pop!' But I was trying to do things, in my context as a soulful artist, as an artist who does kind of gospel-influenced soul music, but do them with pop melodies and pop themes, and production that spans pop music."
The resulting album nods to McCartney (the piano ballad Where Did My Baby Go?), Buckley (emotive song-prayer Show Me, the album's new single) and the Drifters (doo-wopping soft-shoe shuffle Slow Dance), while remaining true to Legend's sense of who he is as a musician and where he wants to take his audience.
Watching him write a song is instructive. Sitting at the piano, he performs what looks to be the audio equivalent of doodling, conjuring up clouds of harmony out of which a tune begins to form, to which he gradually appends words, selected at first for their sympathy with the music's mood rather than with a pre-ordained notion of what the song should be about. It seems random, almost haphazard, and it is clear that an emotional connection is at the root of what he writes.
But Legend's background means he is not prepared to leave the way his music is interpreted or presented to chance. After graduating, he worked as a management consultant in New York for the better part of three years. The upside of a musician having such experience is obvious: who better to keep an eye on how his career is progressing? But is it possible to remove the cool, analytical businessman from the equation when it's time to write and perform music that has to be felt and meant, not planned and strategised?
"I'm always trying to just do things the best way I can," he says. "As a musician I'm very simple: I just go with my heart and I go with what feels right. Then, once the music is made and I'm thinking about how to market it, I get into strategic mode. But I really do separate those two sides: I really think just about the music when I'm making the music. But when I'm done, when the album's ready, when I'm thinking about trying to get it out there to the people, then I do start to think strategically."
As labels struggle to find new ways of making money from selling recorded music, artists with an awareness and understanding of how marketing works, and who grasp that music is just one aspect of what they do, have the upper hand. It should surely follow that someone with a business background will be better placed to capitalise.
"It's an advantage," he shrugs, "but, you know, if you don't make hot records, it don't matter that much. That's the only advantage I'm concerned about. The most important thing is writing better songs and making better records than everybody else."
And not just his own records. Legend has set up a label, Home School Records, and made the British rapper/singer Estelle his first signing. The pair met five years ago when Estelle approached Kanye West in a Los Angeles restaurant, introduced herself and asked who John Legend was; he turned out to be sitting at the same table. As well as "executive producing and overseeing" her forthcoming LP, Legend has also signed his own brother, Vaughan Anthony ("His sound is somewhat similar to mine, but with a slightly more contemporary edge"), and two rappers.
Despite his evident workaholic, micro-managing tendencies, Legend rarely flags. He manages eight hours of sleep a night, keeps healthy with a sensible diet and exercise regime, limits himself to "an occasional smoke" and drinks infrequently. He has managed to keep his private life out of the newspapers, partly, he believes, by never having dated a famous woman, and partly because New York has a less ferocious tabloid culture than London or LA. For Legend, work is as important as play.
"It's amazing to me, but when I talk to my label, they're like, 'Oh, John, you work so hard!'" He shakes his head, dumbfounded. "It always amazes me that I stand out among other artists for working hard. Shouldn't everybody work hard? Why wouldn't they work hard? You dick - this is your shot! Ultimately, it's your career. If you don't seize this opportunity, it's going to go away. You might not be as smart or you might not have as good a record, but there should be no excuse for not working hard."
· John Legend appears at the Hammersmith Apollo on June 29. Box office: 0870 606 3400