Jazz Festival preview: Meanwhile, in Tin Pan Alley ...

Call it retro, call it postmodern - call it anything you like in fact - but contemporary jazz isn't really contemporary any more. Instead, it's mostly hurtling ever backwards in a kind of fast-rewind through the styles of the last five decades. For a new artist who wants to be successful, a refuge offered by the past - in, say ,the musically dexterous world of post-war small-group swing a la Nat "King" Cole - may therefore seem as good a place as any to pitch up. This process partly explains the incredible success of the Canadian pianist and singer Diana Krall - the biggest new name in jazz - who headlines an Oris London Jazz Festival concert at the Barbican on Thursday. But Krall isn't just a symptom of some cultural malaise: she's really, really, good. Her voice is a dream of close-miked, breathy expressiveness, her piano playing swings like the clappers, and she has impeccable jazz credentials. But why does she have to sound like 1952?

It may well be that there isn't much choice. The modernist line that stretched from Coleman Hawkins, through to Charlie Parker and Miles Davis, and on to John Coltrane and Ornette Coleman, along with the seemingly boundless formal experimentation that accompanied it, ran out years ago. Free improvisation - jazz's version of the end of history - is now 40 years old. Even in the margins of the avant-garde, the trend is towards crossovers with contemporary classical music, as if jazz in itself is no longer sustainable. The retro aesthetic is also more complicated than it first appears, and worthy of several Cultural Studies dissertations. All over America, young people are now dancing to old swing records and to new bands who copy the repertoire, in a strange movement that somehow mixes the subculture of serious piercings and tattoos with Glenn Miller and the Lindy Hop.

Diana Krall's albums for the Impulse label regularly top the jazz charts, and in the US she actually gets played on the radio, where the dominant "Smooth Jazz" format is so anodyne that it makes even the very mellow Krall sound a little spiky. In the UK Krall has moved from support slots, to headliner at Ronnie Scott's, to a main concert attraction, in little more than two years. And while her winning style may be stuck in the groove cut by the "King" Cole Trio way back when, it works. So why fix it?

"I don't really like categories, but I'm coming out of a traditional approach," says Krall, when I talk to her by telephone at her family's home in Vancouver. "I'd prefer to call it acoustic jazz, but I keep doing different things. For instance I've just finished recording on a Christmas album with Celine Dion, and also recorded with the Chieftains. I'm trying to come from the jazz tradition, but that doesn't mean that it's retro."

Diana Krall, who will be 34 next week, insists that her chosen style derives quite naturally from her family background in British Columbia. "I grew up listening to everything from Puccini to George Formby," she says. "My dad collects old 78s and cylinder recordings and I heard a lot of music in the house, from Fats Waller and Connie Boswell to Peter Frampton and Elton John. It was eclectic, but I always gravitated to jazz. I had a band director at school who turned me on to Charlie Parker and Bill Evans, and that was it."

Her repertoire focuses on "standards", the Tin Pan Alley songs that have fed jazz for much of this century, and whose vocal traditions were defined by singers such as Billie Holiday and Ella Fitzgerald. It's a hard act to follow, and one that most female vocalists these days fail to live up to. "I don't think I make the songs new," KralI says hesitantly, when asked to account for the way she approaches standards. "I don't really know what to do with them, but I just find things in the lyrics that make sense to me as a young woman, and I try to interpret their areas of experience. They've been interpreted by jazz musicians as well as vocalists, and harmonically they're great blowing vehicles. Lyrically, it's like interpreting a play. I can feel a story in it, and there's a lot of theatre involved."

The sense of theatre came across in her Ronnie Scott's season earlier this year. Krall has a modest but commanding presence, and she talks to the audience between tunes with an easy intimacy that very few others could carry off, even in a context as traditionally confessional as that of the female jazz singer. At some point during each set, Krall sits demurely at the keyboard and lets the musicians of her trio have a rest while she takes on a solo. She doesn't have a big voice, and she never tries to stretch it by scatting or forcing vocal effects. Instead, she leans in to within kissing distance of the mike and whispers the typically lovelorn lyric as confidentially as if she were talking on the phone to her best friend. Her warm, seductively accented intonation does the rest. The emotion in the lyrics bubbles up like spring water.

It may not be the future of jazz. But then again, what is, other than some other version of the past? As Diana Krall slow-burns her way through "You're Getting to be a Habit with Me", and the consoling, flickering- fireside heat of her voice is brought into sharp contrast with the rather icy eroticism of her cool looks and presentation, postmodernism almost begins to seem like a good thing.

Diana Krall Trio with Fred Hersch: Barbican Centre, EC2 (0171 638 8891), Thursday.

The Oris London Jazz Festival continues to Sunday 15 November; see Critics Choice, page 15, for next week's other highlights.