Remember Tracy Chapman? For a brief while, 14 years ago, she was everywhere - a powerful, clear voice talkin' about a revolution at a time when Reagan, Thatcher, the Berlin Wall and apartheid all appeared indestructible.

Performing at Nelson Mandela's 70th birthday concert at Wembley Stadium back in 1988, Chapman seemed to speak for a generation of would-be radicals who came of political age too late for Paris 1968 and too early for Seattle 1999 . Aged only 24, she produced not just a one-off memorable song, but a body of work - including Fast Car, Behind The Wall and For My Lover - on an album that many of us still play.

"People really wanted what she had," said David Kershenbaum, who produced her first, eponymous album. "And they weren't getting it. She got there at the right moment with stuff that was good."

But it was a music and a message that managed both to be of their time and to endure beyond it. We carried on listening to her early work even as her face faded from view. Her second album, Crossroads, released just a year after that memorable debut, did well enough, but failed to lodge itself in the collective memory in the same way.

For those who have been following Chapman's career over the past decade, she never went away; there have been world tours, four albums and a whole raft of benefit concerts. But the rest of us are stuck with a sound and an image of her that dates from the late 1980s: all pert dreads and protest lyrics.

Today, aged 38, she boasts a mane of hair that comes halfway down the back of her corduroy jacket. With high cheekbones and smooth, dark skin, you might recognise her in the street, but it would take you a short while to riffle through your mental Rolodex before you matched the face to the name. For the past three months she has been working on her new album, Let It Rain, in Sausalito, near San Francisco, along with British producer John Parish (who also produces PJ Harvey and the Eels).

Chapman emerged at a highly politicised time for pop music. With little organised, effective opposition to the reactionary drift in politics on both sides of the Atlantic, musicians became a key mobilising force in countering the greed-is-good consensus that had taken root during the 1980s. Through Live Aid, the Mandela concert and the Amnesty tours, these people - among them Bob Geldof, Sting, Youssou N'Dour, Bruce Springsteen - espoused the return of morality to public discourse when everything seemed to be subordinated to the pursuit of private affluence.

Songs such as Chapman's Behind The Wall spoke directly to these popular concerns. The track's description of a neighbour listening to the domestic violence next door, too jaded to do anything about it, only to see the ambulance coming to take the victim away, is powerfully understated: "And the police said/I'm here to keep the peace/Will the crowd disperse/I think we all could use some sleep."

As recently as three years ago, Chapman said, "I think it's important, if you are an artist, to use your music to stand up for what you believe in." Today, it's a statement that she would rather qualify; she is less keen to single out herself or her profession for any particular political responsibility. "That's what everyone should do with their lives," she says, "stand up for what they believe in, or try to do some good in the world. I don't think artists have a greater responsibility than anyone else."

Chapman was in Jamaica, performing at the One Love Bob Marley All Star tribute in Oracabessa, when a new generation of protesters brought Seattle to a standstill in 1999 over globalisation and unfair trade. A reporter suggested to her that she should have been there instead of in the Caribbean. "Part of me says you're right," she told him. "But I am a musician and a songwriter, rather than an activist. I don't have that much time."

Chapman's voice remains the most distinguishing feature of the new album, as it is on every one - a distinctive, husky contralto that sits somewhere between Macy Gray and Suzanne Vega. But the same cannot be said of her lyrics. If the dominant mood of her early work was political, the overriding impression of this album is more spiritual. It is a distinction that Chapman does not herself acknowledge. "This record has lots of contemporary issues," she says. "The first record is seen as being more social commentary... more political. But I think that's just all about perspective."

There is some truth in this. The spiritual and the political are arguably at their most resonant when they are mutually reinforcing, and not exclusive. That said, compare her first album with her most recent, and the shift in her priorities as a songwriter is self-evident. Compare, for instance, the lyrics to Why? from the first album (Why are the missiles called peacekeepers?/When they're aimed to kill/Why is a woman still not safe/When she's in her home?) with those of Say Hallelujah on her upcoming record (Have mercy/It's a wonderful life/Eternal rest for the weary/mourners party tonight).

Elsewhere on Let It Rain, tracks called Broken, Happy and Goodbye talk of "searching for a new soul", a warning that "not truth or transcendence will set you free" and a request to "give me hope that help is coming when I need it most". There is an introspective, almost hymnal quality to it all; it's the kind of music you might want to shake a tambourine at or clap along to, folk music that owes more to the traditions of Pentecost than protest.

None of which should suggest that Chapman has become a-political. Her views on the fallout from September 11, for example, reveal a mind that continues to be critical and inquiring. "It almost seems to me there are no words for the horror, not just for that particular day but even now... I think we're screwed... globally. This particular turn of events, and everything that comes with it, it's set us back culturally, socially, 100 steps."

"We do need to think about how we have security - everyone has a right to that - but we also need to think about how we maintain civil rights and personal freedom. What determines our diplomatic policy, what role is this country going to play in the rest of the world? But, unfortunately, from what I can see, there has been very little space for that kind of dissent. Not even dissent, but very little space for dialogue."

The only overtly political song on the new album, the one most reminiscent of her earlier work, also happens to be the best - Hardwired is a broadside against the pervasive nature of consumerism. "Your wants desires/needs and wishes/will be duly noted/ processed filed and catalogued/labelled and encoded/ turned into sitcom dialogue and advertising slogans."

"Maybe it's naive to say," she says, "but it almost seems like, in the past, people tried to sell you something you would actually need, like a hammer or a broom or a toothbrush. But now there's this notion that they can sell you anything. And all they have to do is convince you that you need it. And not only will you be content with that, you might also degrade or debase yourself in some way so that you can have it. And that just seems even more corrupt than selling something no one really wants or needs. They subvert people's real wishes and desires. Not only do they empty their pockets, but they may in the transaction lose their real sense of self."

Tracy Chapman hates interviews. When she started out, says her publicist, "She just used to bend her head and say 'Yes' and 'No'." For several years, she stopped doing them altogether. "There's a time and place for everything," she said a few years ago. "And my focus is music. So that's what I prefer to spend most of my time doing, and not talk about making music."

The problem is not, as some have claimed, that Chapman is shy or standoffish. By the day's end, she has invited everyone to a friend's gig in a bookshop downtown. The problem is that the skills you need to be a good singer and songwriter are not necessarily the ones that make you a good self-publicist. She rarely talks to the audience during her gigs. "Generally, there's not anything to say to this mass of strangers that's significant or not superficial," she told Rolling Stone months after she'd first become famous. "So I generally don't say anything... If, somehow, I could walk around invisible when I'm not on stage... "

Paradoxically, given her views on the cynicism of the marketing world today, back then even Chapman's silence became a commodity. "We wanted to be guarded and gain respect, and you make things more important by limiting their quantity," says her former manager, Elliot Roberts, who discouraged Chapman from talking on stage. "I don't want to make it seem contrived on any level because it's not. But is there a plan? Yes. Do we execute it? Yes. Have we been lucky so far? Yes."

So, even if Chapman is not awkward herself, her conversation certainly is. "I don't know," was an answer she gave to the questions: "Who were your musical influences?" "How did it feel to be propelled to stardom after the Mandela concert?" and "What would you regard as your political priorities at the moment?"

Those questions that she does answer are exhaustively qualified. Take this one exchange:

Guardian: "Cleveland, Ohio, in the 1960s and 1970s must have been a particular time and place to grow up. What was it like?"

Chapman: "Well, everywhere and every time is particular. I don't know. I didn't grow up any place else."

G: "But some places and times are more particular than others."

C: "Yeah, I guess so."

G: "So what was it like?"

C: "Oh, I have nothing to compare it with. I never travelled when I was younger."

G: "I'm not asking you to compare it. I just wonder whether there was a lot going on?"

Cleveland, where Chapman was born in 1964, was, she finally admits, a very particular time and place to grow up. With the focus shifting from civil rights in the south to economic rights in the north, industrial cities such as Cleveland were the new focal points for both racial tension and black progress. In 1966 the city saw five nights of rioting; a year later it elected Carl Stokes, the first black mayor of a major US city. "It was a difficult place, for me, to grow up," she says. "It was a very racially divided city, and in most places public schools were forced to desegregate, and white people protested and tried to stop buses. That was a controversial time. We always had trouble. Teachers weren't paid very well and they went on strike."

Her parents divorced when she was four. Tracy and her older sister lived with her mother, who, having refused child support from her father, raised them on welfare while working in low-paid jobs. "There wasn't much to work with," says Chapman. "We always had food to eat and a place to stay, but it was a fairly bare-bones kind of thing."

Her mother would explain the political context for their poverty. "As a child I always had a sense of social conditions and political situations," she told Rolling Stone. "I think it had to do with the fact that my mother was always discussing things with my sister and me - also because I read a lot. A lot of people in similar situations just have a sense that they're poor or disenfranchised, but they don't really think about what's created the situation or what factors don't allow them to control their lives."

By the age of 14 Chapman had written a song called Cleveland '78, addressing the issues, as she saw them, of the day. "People were finding out about asbestosis and Andrew Young [the US's first African-American ambassador to the United Nations] was in some controversy and I had something in there about flying saucers."

Chapman was awarded a scholarship to an Episcopalian prep school in Connecticut, and from there went to Tufts University, Massachusetts. She chose Tufts because she wanted to fulfil her lifelong ambition to be a vet, but soon after she arrived there she changed her degree to anthropology and African studies, graduating in 1986. One summer, when she could bear her summer job mowing lawns no longer, she started busking. "It's worse than playing in a club, because there's so many distractions," she once said. "You can feel rejected if people don't stop, so you have to kind of insulate yourself."

Her contemporaries noticed her potential. One classmate got her to send a rough tape to his uncle at CBS records. The rejection letter advised her to tune her guitar before she sent another tape. A fellow student recommended her to his father, Charles Koppelman, then president of SBK music publishing. He in turn introduced her to David Kershenbaum, who produced her first album for Elektra, after other producers had turned her down.

A few months after the album's release, Chapman appeared at Wembley Stadium in the tribute to Mandela, who was still behind bars. The event was televised, and Chapman was the star of the show. Two days later, her album had sold 12,000 copies and topped the UK charts. She won best international newcomer at that year's Brit awards and three Grammys (best vocal pop performance, best contemporary folk recording and best new artist). Almost straight after the Mandela concert, there was an Amnesty International tour with Peter Gabriel, Bruce Springsteen, Sting and Youssou N'Dour, which took them around the world - the first of many benefits she would play over the years to support causes as varied as Farm Aid, human rights in Tibet and Cambodia, and PEN America, which supports writers and literary freedom, not to mention a number of rallies celebrating Mandela's release.

Early on, it seems, Chapman made a decision to try, wherever possible, to ringfence the music from the money. "I decided to do whatever I could to be sure the business side of music didn't intrude on the creative part," she has said. Nor does she suffer interference from producers or corporate representatives. "I can't think of anything worse, really, than to try to live up to someone else's expectations of what you should be. You don't make art by consensus."

I remember talking to a man who had been involved in racially integrating a North Carolina lunch counter as a youngster in the 1960s, who described the sense of "elation and celebration" as he took his seat under the Whites Only sign. "It was a cruel hoax," he said, "because people go through their whole lives and they don't get that happen to them and here it's being visited on me as a 17-year-old. It was wonderful but sad also, because I know that I'll never have that again."

I wondered whether that was what it felt like to be Tracy Chapman - to be burdened with the weight of your own achievements. To feel that people would rather freeze you in a particular time, when you had meaning for them, rather than let you move on to a place where you have meaning for yourself. "What can I do about it?" she says. "Nothing. There are things I worry about, but that's not one of them. It's not that I don't sense that there are people who would like me to be more like I was at that time. But I don't feel it as a pressure. I wouldn't choose my direction based on that."

Quite what her direction is, however, is not obvious to her. "I just started out with a certain number of songs, so I haven't had much time to think about what was going on as a whole . . . Some things are coming together, but I'm not all that clear if there is any overriding direction. I'm only just starting to talk about the record and it's difficult. When I think about it now, there seem to be subjects that do recur, certainly love, death, identity."

The one big idea she did have for the album - that on some level it would reflect and inform the musical scene of her adopted neighbourhood - failed. "I really wanted to try and create community, and my initial approach was to try and put a band together with players from the San Francisco area," she says. After six weeks of auditioning, she gave up.

When recording her other records, Chapman travelled to Los Angeles and went home to a hotel room every night; this time, she got the other musicians to come north to San Francisco. "It's all about finding the balance, and I'm just working on that," she said recently. "If I don't take time for that part of my life [walking the dog], then I don't have anything to offer musically, because I don't think most people want to hear songs about life on the bus or in the hotel."

The security of domesticity, along with a few home improvements - she recently had a studio built in her house - may have contributed to the more spiritual feel of the album, she says. "A lot of these songs started to develop in my house. It's the first time I've ever had a dedicated space in my house for making music. It gave me a lot of freedom to work on things and work out ideas. Maybe coming out of a completely intimate environment like that, some of it translated to the record."

Making music remains an essential component of who she is. "I realise that, aside from waking up every morning and eating and getting dressed, one of the things that I have done most consistently for my whole life is to write songs and play guitar and make music. Right now, it's my vocation and it's my passion. I'm fortunate that I've been able to do my work and be involved in certain organisations, certain endeavours, and offered some assistance in some way. Whether that is about raising money or helping to raise awareness, just being another body to show some force and conviction for a particular idea. Finding out where the need is - and if someone thinks you're going to be helpful, then helping."

And who does she think needs most help at the moment? "I don't know... The thing is, unfortunately, it never ends."

It may never end, but it does change. Power relationships do shift. After all, she wouldn't be playing a Free Mandela concert now. "I don't know what it is that shifts," she says. "Public sympathies shift. Politics shift. But the need never changes."

· The single You're The One is released on eastwest records on October 14; the album Let It Rain is released on October 28.