Ahead of next Wednesday's sold-out solo show at Dublin's Olympia Theatre, the usually enigmatic PJ Harvey pours forth to Kevin Courtneyabout her new subdued sound and the pressures and pleasures of going it alone.

'I'VE never had a problem getting into that process of being able to embody the song. I can't describe it any better than that. I always feel a sense of becoming the song. It's not that I change into another person, it's more that I leave behind the mind and just let the music just become me."

Polly Jean Harvey has emerged from her eyrie in Dorset and come up to London to chat to The Ticket about a few of her favourite things. The Mercury Music Prize-winning singer-songwriter doesn't do that many interviews.

In an age when pop stars regularly stagger around in the glare of the flashbulbs, the 37-year-old has managed to maintain her enigma - not bad for a woman who has spent the past two decades baring her soul and revealing her darkest fears over the course of eight powerful, passionate albums and countless memorable stage performances.

Today, she's in London to see some friends playing a gig, but next Wednesday she'll be the one on stage, performing a sold-out solo show at Dublin's Olympia Theatre. No longer a hungry young indie girl with a guitar, PJ Harvey will be performing alone, without a safety net, delivering her songs on a number of different instruments, including the one that's been fuelling her passion lately - the piano.

"I sort of move around to different stations on the stage," she says. "I think the shows are very very different, and I find that the sort of dialogue between myself and the audience is much greater - in all senses of the world, both verbally but also in the sort of emotional feedback that you have. And the shows are very warm and happy events."

Harvey's new album, White Chalk, marks another radical departure for an artist who has never stood still and has never given in to musical complacency.

For this album, she switched emphasis from guitar-led riffology to piano-based balladry, and the result is an intense, original and compelling work that sounds like nothing else going on around it. Like Björk, Polly Jean Harvey seems to be able to weave her own musical universe and make it feel like a truly phantasmagorical place to be. From the storming emotion of The Devil to the keening pleading of The Piano, White Chalk is an album that delves into the deepest recesses of human feeling, and comes up bearing musical treasures aplenty. Harvey has taken numerous different routes on her rock'n'roll path, and they seem to have led her naturally to this point in her career.

"I wasn't aware that it was something that I was striving towards over a long period of time. I can remember years and years ago seeing Neil Young do the MTV Unplugged. And it blew me away, that voice, particularly the first six or seven songs which he played on his own, and he was playing guitar and harmonica, and then he'd be playing the harmonium.

"And I've never forgotten how powerful that was, and I've been a huge fan of his all my life, and maybe that planted the seed - it possibly did."

Not everyone can do a solo show with the power of Neil Young in his prime. The challenge, she says, was to be able to "present a show that would remain interesting". So she thought about all the solo shows she'd seen, and what she liked and disliked about them, and learned that, with just a little thought, she could do justice to the songs.

"I wanted it to be a more theatrical piece, where the stage would look interesting visually, and I'd have these stations that I'd move to, to play different instruments. I just wanted to make the stage into a comfortable environment for me to feel at home to do a more intimate way of presenting the songs. And I've found that it's a wonderful platform for me to do a retrospective of my work. I'm not just playing the new album. It's everything I've ever done."

To make her - and presumably the audience - feel more comfortable, Polly is using a few objects from her home in Dorset as stage props. All very cosy, but this isn't to suggest that she'd rather stay at home in splendid isolation, far from the madding rock crowd.

"Well, I wouldn't want people to think I shut myself away like some sort of a hermit. Cos it's not like that. With the music that I make, people imagine I live in a cave at the edge of a cliff, and go out about once a week, sort of thing. But where I live in Dorset is quite a vibrant place, really, full of a lot of interesting artwork going on, full of a lot of interesting people.

"I make the most of that. We've got a lot of great art centres down there, great cinemas, wonderful group events happening around the arts, so it's a very rich lifestyle, I would say."

As well as being a multi-instrumentalist, Polly is a multi-disciplinary kind of girl, and she makes no distinction between different artforms. She grew up in Corscombe, Dorset, the daughter of a sculptor and a stonemason, and completed a foundation course in Yeovil Art College. She was all set to do a degree in sculpture at St Martin's College in London, but recorded her debut album Dry instead. But Harvey's music has not been visual art's loss - she still sculpts and paints, often working out her musical and lyrical ideas through these other media.

"It does go hand in hand with making music, I think, just making things. And these days, I tend to draw or make things around a song I might be writing, because it all feeds into each other. And also I've noticed over the years that I'm very much a visual ideas person, so songs are very often visual pictures I have first, which I then make into a song, but it's almost as if they are short movies, and I can see them. I see the song and then I make the song."

Anyone who's experienced the full palette of Harvey's music, from the raw, exposed scream of Rid of Me to the swamped emotions of To Bring You My Love to the sweeping canvas of her Mercury-winning Stories from the City, Stories from the Sea, will know that Harvey puts a lot more than notes and words into her music - she puts everything she's got into it.

Even when she's collaborating with other artists, she puts her all into it. She has worked with everyone from Thom Yorke to Nick Cave, from Josh Homme to Mark Lanegan, and each project has brought out a different facet of her talent. She's been managed by Paul McGuinness since 1994, who she says is "always there for me", and in 2004 she produced and wrote songs for Marianne Faithfull's album, Before the Poison.

She's currently working on a project with long-time collaborator John Parish, completing business begun with their 1996 joint effort, Dance Hall at Louse Point.

"I think I feel a sense of joy from having made something, and that's very addictive. I get enormous pleasure from helping the songs evolve and become something that is almost tangible and lives on, and that's a wonderfully rewarding feeling." The new album, she says, came out of a long period of meticulous searching and a period of painstaking trial and error.

"I was looking for a long time for something to excite me. Because I've been writing songs now for a long time, it becomes harder to find things that really excite my desire for finding new material. Through continually looking, I eventually found a new way of singing and a new way of playing."

While she didn't quite run the gamut of trying out flugelhorns and Peruvian nose flutes, she did go through a lot of different instruments, styles and lyrical ideas in her quest for musical fire.

"I put an enormous amount of work into my work," she says. "I take it very seriously. I read, I study, I look at metre, I look at different ways of writing poetry, I look at the English language, I study it, I look at old folk songs, I gather as much information as I possibly can about the nature of songwriting, and I believe it's my life's study. And so each project that I do I feel I'm getting a little bit more understanding of the framework of what I do with my life."

Almost 20 years into her career, Harvey also feels older, wiser and more alive than ever.

"I feel just wonderful, I love the whole process of ageing, It's so conducive to becoming a better human being. You become more humble, but you're also able to see things with much greater perspective, and life just becomes richer and richer."

PJ Harvey plays Dublin's Olympia Theatre on Wednesday