Twelve years of hard graft are, at long last, beginning to pay off for the Esbjorn Svensson Trio.

With a string of awards to their credit, a top-20 chart hit in their home country of Sweden, and a burgeoning European fanbase, EST have defiantly emerged from the underground scene to rapturous applause.

But ask band leader and pianist Esbjorn Svensson to describe the sound which has made them so successful and you'll find him lost for words.

"That's always a problematic question," he says. "In general, I find you can't explain music with words, especially our music."

Svensson first met Magnus Ostrom when the pair were just three years old. ostrom took up the drums, while Esbjorn says he only started playing the piano by default because his parents didn't own any other instruments.

They grew up listening to British rock bands such as Slade, Deep Purple and The Sweet, though this isn't self-evident when listening to EST's latest album, Viaticum, which has a distinctly electronic feel in places.

"We're from the synthesiser generation, so we're no strangers to electronic music," says Esbjorn. "We love the rhythmic complexity of artists such as Squarepusher and Aphex Twin. But our music is still rooted in the tradition of the acoustic piano trio. We tried to develop the inspiration their music gave us in our own way."

Now Esbjorn professes to be "digging" a lot of Bach and Bella Bartok. Though he admits his influences never really equate with the EST sound. It is, he says, something you have to experience for yourself.

"All I can say for sure is that our sound is really melodic. There are no vocals and the rhythms may be technically complex but it's not hard to listen to at all."

Though Magnus and Esbjorn had worked together on and off over the years, EST did not take shape until bassist Dan Berglund joined them in 1993.

Since then, the trio have delved deep into the uncharted waters between peripheral electronica and the acoustic jazz piano tradition, developing an almost telepathic talent for live improvisation.

"We approach every concert as if it were an improvisation in itself," Esbjorn explains. "We don't use set lists, which means we're totally free in what we do. It takes a lot of concentration and I think our audiences can tell we're not just following a routine."

Forget any preconceptions you might have about tuneless jazzimprov noodling though: EST's live shows are highly accessible and have seen audience numbers swell dramatically in recent years.

"Initially, I thought we shouldn't play anything bigger than jazz clubs but you can't do that forever," he concedes. "I'm used to playing bigger shows now and I really like it.

"Even in a 2,000-capacity venue, it's still possible to make it feel as though you're playing in someone's living room."

Support comes from the Eivind Aarset Trio, who specialise in their own distinctive brand of electronically-embellished jazz.

Starts 8pm, tickets £16/£14/£10/£6.