Liane Carroll was in the make-shift make-up room at Brecon Jazz Festival, preparing for a BBC broadcast, when she heard a sound that made her sit up and gasp, �Who�s that?�

Liane Carroll was in the make-shift make-up room at Brecon Jazz Festival, preparing for a BBC broadcast, when she heard a sound that made her sit up and gasp, "Who's that?"

It was one of these moments that's part disbelief but also part recognition. The sound was coming from the piano Brian Kellock was playing with the Scottish National Jazz Orchestra.

Carroll and Kellock had recently become acquainted and the effervescence Kellock was bringing to SNJO's performance of Rhapsody in Blue that day in August 2006 was somehow familiar.

The fizz that Kellock brings to every song, diving into its emotions and revelling in the improvised possibilities that its structure offers, is much more familiar now that Carroll and Kellock have paired up professionally.

They have an imminent tour, supported by the Scottish Arts Council - on which two nights are going to be recorded for a live album, courtesy of the ever supportive Jazz Aberdeen, at the Granite City's Blue Lamp venue - and Carroll feels like a teenager waiting for a date. Musically speaking, as this happily married mum points out.

"I just love the raw immediacy of Brian's piano playing," she says. "It's beautiful but it's a kind of brutal beauty. It's very physical and you can almost wrap your arms round the music, which for a singer is a great thing to feel."

Carroll is no slouch as a pianist herself. As well as winning the Best Jazz Vocalist category at the BBC Jazz Awards 2005, she took the Musician of the Year title at the Parliamentary Jazz Awards 2008 on the back of her outstanding vocal and piano album Slow Down, where Tom Waits and Laura Nyro songs sit easily alongside jazz standards.

Indeed, she began her career virtually straight from school as a piano and keyboards player. It was the look rather than the sound of the piano that first attracted her to the instrument, however.

"There were a few music shops near where we lived in London and I'd see pianos in their windows and pester my mum for one," she says. "But it was a choice then between a piano and a cement mixer because I had a real thing for them, too."

Her mum, who had been a professional singer - "before the shock of having me put her off" - and had sung with the Ken Macintosh Band, sent Liane to piano lessons from the age of three.

"My dad was a semi-pro piano player but we didn't have a piano in the house until I was about six. So I had to go round to my Uncle Bill and Auntie Ada's to practise, and I did practise. I had to because my teacher was very old and very strict but that was good for me because I took all my grades, which were the only exams I was ever interested in taking."

At the age of 15, with her O-levels behind her, Liane had a meeting with her headmistress, at which her school attendance record, her preference for her Saturday job in a music shop and the wasting of each other's time were discussed.

The upshot was that Liane should get on with what she really wanted to do, so the music shop job expanded through the week and she got a gig with a local jazz/rock band. It was the beginning of a 20-year period of dues-paying, during which - to give the potted version - she played hotel cabaret gigs, toured as pianist and backing vocalist with Gerry Rafferty and worked all over Europe with a drum'n'bass band.

"I'd always loved jazz," she says. "I used to subscribe to Jazz Journal magazine from when I was 10 or 11 and I had a real crush on Scott Hamilton because I liked his saxophone playing. He also had a moustache and he looked so sophisticated to me.

"My party piece was Hello Dolly, which I learned from Louis Armstrong and used to sing to the drivers in my grandparents' transport cafe. So I was always out of step at school anyway. When everyone else was getting into Saturday Night Fever, I thought it was a poor substitute for James Brown. But I wasn't so much of a purist that I'd turn down work because it didn't suit my tastes."

The Gerry Rafferty tour in the mid 1990s she recalls as "heaven", being onstage with 11 musicians every night and learning songs directly from Rafferty, whose voice she says was bigger and warmer than his records suggested.

She also worked at a different end of the musical spectrum with saxophonist Trevor Watts' jazz-world music group Moire Music and can rattle off tales about being mis-booked for weddings and country and western clubs where sheer instinct and the development of a broader musical appreciation got her out of a fix.

It was around the turn of the millennium, with her 40th birthday round the corner, that Carroll began to get noticed as a singer-pianist rather than the other way around. From being the show-off who entertained transport cafe customers as a primary schoolgirl she became quite shy and it took her some time - and her introduction to Dutch courage, she concedes - to be the focal point vocally in public.

"I'd get so involved in the emotions behind some songs that I think I was scared of showing too much of myself," she says. "I can still get emotional on a gig. Some songs, like If I Loved You, which I listened to on the Carousel soundtrack with my nan, just bring out special memories.

"It's funny because I stopped drinking about six months ago and I worried I might not feel the emotion in music so strongly any more. But actually, I feel it more now. It's a matter of controlling it, I suppose, so that I don't blub all over the front row."

Part of the reason for her and Kellock hitting it off so well is their shared liking for spontaneity.

Kellock is seldom happier than when being given a tune title and a key and counted in, and Carroll doesn't go in much for forward planning. The track list for her Slow Down album was still a mystery the day before its recording and at least one track, Lazy Afternoon, was re-learned on the spot courtesy of iTunes.

"It may sound daft but I prefer being unprepared because if I get the opportunity to change something, I'll take it or I might lose confidence in the arrangement or start thinking about it too much," she says. "I always want the music to stay fresh and honest.

"With Lazy Afternoon, the idea just popped into my head. I'd loved it when I was 18 and then Wynton Marsalis did that great version on his Hot House Flowers album. But I hadn't sung it in ages and had to have a quick refresher course, and it worked out okay really. All that's not to say that, when Brian and I get together, we won't know what we're going to do. We will. And we might even stick to it."

Liane Carroll and Brian Kellock play Carnegie Hall, Dunfermline, on Wednesday, October 29; The Blue Lamp, Aberdeen, on October 30 and 31; the Regal Theatre, Bathgate, on Saturday, November 1; Eden Court, Inverness, on Sunday, November 9, Perth Theatre on Monday, November 10; Royal Concert Hall, Glasgow, on November 20; The Lot, Edinburgh, on November 21; and Hospitalfield House, Arbroath, on November 22.