An emergency replacement for the rapper Nas on Jools Holland's Later TV show, KT Tunstall came, saw, conquered - and rocked. The Scottish singer, who is, quite literally a one-woman band, is now tipped to become the next big thing. She talks to Brian Boyd

The Akai Headrush foot pedal is a wonderful thing. Just ask KT Tunstall.

The Scottish singer, widely tipped to be a big breakthrough artist over the next few months, didn't want to be "another girl with a guitar" so she invested in the career-changing effects pedal. "I couldn't do any more shows with the guitar, I wanted a band sound, but didn't know how to find one - but I did when I got the Akai," she says.

"It's a fantastic machine, how it works is that when you play something or sing something, you can loop it up so it repeats the sound, then play something on top of that loop as many times as you want. You soon have yourself your own demented one-man band - it's great."

KT and her Akai made their début on Jools Holland's Later show earlier this year - her performance has been talked about as one of the programme's highlights of the year. "I was playing a gig in Sheffield and just after finishing I got a call from Jools who explained to me that the rapper Nas had dropped out of the show at the last minute, so he asked me to replace him. It was just me, my guitar, my Akai and for percussion I stamped all over this tambourine so the sound was really full. The day after I received hundreds upon hundreds of e-mails - from jazz trombone players to young indie kids. There was no pattern to the reaction at all."

It's a given in the music industry that a new female artist will only be talked about in terms of previous female acts - and so far, Tunstall has been described as "the link between Norah Jones and Björk" and also "a cross between Joni Mitchell and Janis Joplin". Her impressive début album, Eye To The Telescope, is a beguiling mix of coffee-house acoustica, skewed jazz, widescreen anthems and an everpresent blues undertow. It sounds like what you might get if the White Stripes were to record an unplugged album, albeit with plenty of loud bits.

A quarter Chinese - her maternal grandmother is from Hong Kong, KT ("it's really just Kate, but Kate just says farmer's daughter to me") was adopted and brought up by a father who is a noted physicist and keen observatory attender (hence the album title - "He'd get us up in the middle of the night to show us Halley's Comet") and a teacher mother "who enjoys making things out of junk".

Classically trained, she excelled at the piano and flute (which she pronounces "fleet" - something which leaves you mystified until you decode her Scottish accent), she got music scholarships to the US and London's prestigious Royal Holloway College, but soon realised the piano wasn't for her.

"When I started writing songs, horrible schmaltzy love nonsense - a complete vomit of puppy love - I realised very quickly that the piano simply wasn't the vehicle to get them across so I learnt the guitar even though I still don't want to be 'a girl with a guitar' type of musician."

After signing a publishing deal with a major label, she was shunted around various other songwriters to come up with co-writes - something she despised. "I get so frustrated with all these so-called singer-songwriters appearing and they don't write their own material, it's all co-writes with some professional production team. That's crap, put yourself on the line instead and do it yourself."

Now 29, she did get a bit of the "but you're over 25" attitude from record companies who obviously prized totty over genuine musical talent. A related attitude now means that she is being dragged into a Norah Jones/Katie Melua/Joss Stone ghetto - something she is firmly resisting. "If someone wants to buy the album to put on a coffee table," she notes archly, "that's fine - just as long as the CD is in the player."

The album was produced by a heavy-hitter in the shape of Steve Osbourne, who has twiddled knobs for U2, New Order and The Happy Mondays. "He picked up on a blues aspect to the songs and put me straight on to an up-to-11 electric guitar. We listened to a lot of old 1920s and 1930s blues records, all that hiss and crackle stuff. Being a female artist, you can find yourself getting pushed into a corner. You're supposed to sound pleasant and well-behaved, so we went the other way - a big influence on me would have been Tom Waits's Bone Machine album. I took very little equipment into the studio because I find that when you have to be inventive you get interesting music. There's a quote somewhere by Tom Waits where he says 'some musicians spend $20,000 trying to get a drum sound like a shoe hitting a bin, why don't they just hit the bin with shoe instead?' and that was a kind of rule for us recording this."

Although she has a voice that's more than capable of show-offy acrobatics, she reins herself in on most every song. "I can do all the vocal acrobatics," she says, "but I try not to. I'm drawn to singers who sing it pure and straight: Patti Smith and Carole King."

Seemingly capable of any musical style - and the album does cover a lot of bases - Tunstall puts her versatility down to her wide-ranging musical background.

"Way, way back I would have been singing hair-metal songs," she says. "Then I really got into Bowie's Hunky Dory album, then I started listening to Ella Fitzgerald tapes and that's where I learnt how to sing, then I got into Johnny Cash and then I started singing with bands from around where I'm from - great bands such as the Beta Band and Dogs Die In Hot Cars. Oh, and I've also sang with Oi Va Voi, who are a traditional Jewish music/hip-hop band. As I said, I don't want to just be seen as a girl with a guitar."

Eye To The Telescope is released today