Acclaimed as a poet, Jackie Kay has turned to fiction - and to a jazz virtuoso with a secret to preserve. Andrea Stuart asks her about the stories of our lives
I'd love to say I'd done something like fish pathology," the Scottish writer Jackie Kay tells me over lunch in Islington, when I ask her about what she read at university. "But the real answer is that it was English." It is a choice that she regards as unbeatably hackneyed for a writer. She need not worry, though; none of the rest of her life could be labelled as predictable.

Kay was born in 1961 in Edinburgh, the product of an inter-racial liaison, and brought up in Glasgow by white adoptive parents. It is tempting to read into these simple facts everything we might want to imagine about Kay's life and work. Indeed, fact and fiction intertwine in her critically acclaimed poetry sequence The Adoption Papers, but Kay resists such an easy interpretation. "People regard The Adoption Papers as much more autobiographical than it actually is. I didn't anticipate the number of people who would come up and tell me their stories. You end up being an adoption counsellor, which isn't what I wanted," she laughs, half exasperated.

"I am adopted myself and that is a fact. But for me it is like saying, 'I was born.' Yet it is an interesting fact, because it gives you so many possibilities to explore, so many identities to play with, so many ways you can make or remake yourself."

I ask her whether this collective fascination with the personal story is a product of our times. She agrees. "We are obsessed, especially in the Nineties, with the narratives of our lives. Maybe this is because as a society we are led by the media, by journalism - particularly the tabloids - and their way of telling stories, which tends to look at real life from the perspective of an individual's story. So when David Beckham kicks someone in a fit of petulance, we suddenly become interested in what his school report can tell us. And Louise Woodward becomes more compelling than half a country starving."

"The Nineties," she muses, "is a very self-preoccupied generation. Even in the context of people's involvement in politics: all the leftists are now acupuncturists; all the activists are in therapy. Our ideas about responsibility have changed. We don't have a sense of being responsible for anyone other than ourselves and our immediate family." Thinking of the ceaseless stream of home-improvement TV and lifestyle columns, one can't help but agree. "It's worrying," she insists, then declares optimistically, "but it will probably go out of fashion again in the millennium and we'll become a more intellectual, outward-looking society."

In an oblique way, her latest book, and first novel, Trumpet (Picador, pounds 12.99), touches on these issues. "In 1989 I read a short four lines in a newspaper saying that the jazz musician Billy Tipton had died," she explains. "At which point it was discovered that 'he' was actually a woman. What touched me particularly was a quote from his adopted son who said, 'He will always be Daddy to me.' It was a story that was both ordinary and extraordinary. Ordinary in that he was still 'daddy', and extraordinary in that the son accepted his father's construction of his identity, and that is both radical and challenging."

Trumpet is a reworking of Tipton's life, traced through the aftermath of the death of his fictional counterpart, Joss Moody. Jackie Kay both uses the "true story", and blows it apart. She writes about Joss from his own perspective, as well as from the viewpoints of his widow, his bereaved son, the household maid, and a tabloid journalist. So there is no single narrative and the one apparently true story - his gender - turns out to be false.

The book's style works like a jazz riff, a literary improvisation on the central melody of Joss's death. By exploring these numerous but ordinary characters, and their responses to such an extraordinary occurrence, Kay manages to reveal the truth that inevitably lurks behind every lie; and the lie that only the truth can tell.

In the middle of writing Trumpet, Kay took a literary detour and wrote an imaginative biography of the great blues singer Bessie Smith. "I was given a record of hers when I was a teenager and I became obsessed with her. She was a great performer, who could hold her audiences spellbound. And the bell-curve of her life is fascinating. She began singing on street- corners, going on to become the richest black woman in America - making $20,000 a week. But then she went into a decline which ended in a road- accident death that everyone has a different version of, like with Princess Diana. For me, she was a sort of role model: all the complexity of her. After all, she was an alcoholic, bisexual, violent; she had a lot going for her, really."

What fascinated Kay about the blues was its narrative, its ability to tell people's stories. This led her to jazz. She describes both forms as a "space of possibility". "When music moves you it strips you bare, beyond being a girl or a boy, black or white, gay or straight, old or young. This music contains so many contradictions, and it doesn't have rigid boundaries, so it is very freeing. In Trumpet, jazz becomes a beautiful way of exploring identity, expressing that process of losing yourself, finding yourself, forgetting yourself and remembering yourself, going backwards and forwards."

"Memory, truth, lies, masquerade, performance; that is what consistently fascinates me." It is no surprise when Jackie Kay reveals that her childhood dream was to be an actress. "I didn't think that I would be a writer; I thought that's what my daughter would be." It wasn't that she didn't write - there was the usual keeping of notebooks with doodled-on covers. "But I really enjoyed reading poems and stories for friends and having them laugh or be moved."

From the ages of 11 to 16, Kay attended the Royal Scottish Academy of Music and Drama. "I loved the theatre and the possibility of being someone else." But she found that there weren't a lot of parts for little black Scottish girls, no matter how talented. So she focused on her writing.

Does she think of writing as a sort of performance? "I think it is. Particularly poetry, which is a performance both for the poet and on the page. When I was small I used to go to Burns Night suppers and I loved it when the knife stabbed into the haggis" - she acts the motion out vigorously, reciting Burns as she stabs - "It was so wonderfully dramatic." Fiction is somewhat different, she feels, but also argues that everything we read is simultaneously performed in our imagination, "which is why we get so upset when we see film versions, because they've never cast them properly."

About her novel, she says: "I want people to want to turn the page. I like stories; stories being told, stories being passed on, stories which have a place, which come from somewhere. It's really old fashioned," she mock-laments, "in this postmodern age."