Over the past dozen or so years Shooglenifty's unique twist on trad has won them an extensive and devoted fanbase not only across Europe, the US and Australasia, but as far afield as India, Malaysia and Japan.

Right now, the Edinburgh-based six-piece are just about at the end of another whistlestop year of touring, taking in France, Denmark, Belgium, Spain, Norway, Ireland, Italy and Tenerife, as well as UK appearances. Previous career highlights include performing for Prince Charles, Nelson Mandela and Emperor Akihito of Japan (not all at once), and playing in Cuba a full year before the Manic Street Preachers' much-vaunted Louder than War gig in 2001. Back in 1996, meanwhile, Shooglenifty became the first band ever to incite a stage invasion at Sydney Opera House.

"We did invite them on stage, though," points out the guitarist Malcolm Crosbie. "Angus [Grant], our fiddle-player, could see that there wasn't enough room for dancing - it's an all-seater venue, obviously - so he just said to the audience, 'Plenty of room up here...', and suddenly we were surrounded by a couple of hundred people jumping around."

Among the current Shooglenifty line-up, the percussionist James Mackintosh is the fourth remaining original member, while the bassist Quee MacArthur and the Tasmanian expat Luke Plumb, on mandolin, banjo and bouzouki, both joined two years ago. The band's collective CV takes in backgrounds as diverse as Crosbie's apprenticeship in alt.rock obscurity, Finlayson's early blues fixation and Grant's childhood immersion in the West Highland fiddle tradition. Beneath their folky-looking exterior lurk electric as well as acoustic guitar, samples and programming as well as "real" percussion, while Finlayson switches between regular banjo and his own customised hi-tech version, or "banjax". All six players, though, are maestros of effects, distortion, feedback and - crucially - improvisation.

The resulting sound marries traditionally based tunes - primarily Scottish in style, but featuring a wealth of other world-music flavours - with the rhythmic energy, inventiveness and sophistication of contemporary dance music. Such a description, though, hardly begins to capture the dazzling multi-layered intricacy, exquisitely jewelled lyricism and intoxicating, coruscating grooves that are Shooglenifty's hallmarks. The band's own, none-too earnest attempts at capsule descriptions include "hypno-folkedelic ambient trance" and "acid croft".

The genesis of this hybrid musical strain can be traced to around 1990, following the demise of celebrated Edinburgh psychobilly outfit Swamptrash. Out of those ashes, five of Shooglenifty's original members - including the mandolin player Iain McLeod - began meeting up for weekly pub jam sessions. The bassist Conrad Ivitsky joined, word of mouth snowballed, and they were offered a weekly residency at La Belle Angele, one of several much-loved venues in the Scottish capital destroyed by last winter's Old Town fire.

>From these spontaneous, freewheeling beginnings, Shooglenifty have since been hailed as one of the key pioneers, and continuing frontrunners, in the field of Celtic/clubland fusion. The Afro Celt Sound System might be market leaders, but where they, by their own admission, have only latterly evolved from a studio project into an actual band, Shooglenifty have been the real deal all along.

"We are the complete opposite of a manufactured band - 100 per cent organic," agrees Crosbie. "That first gig at La Belle, there were six people there apart from us. It was the middle of winter, and we were all huddled around this electric-bar fire in the middle of the floor. By the time we actually migrated on to the stage, a couple of months later, there were so many people coming that we had to start using a PA. It really was just a session that kept on evolving."

Despite this absence of calculation or contrivance, however, there was no mistaking that something unusual was happening with their audiences. "You just can't argue with that many people having a good time - we were obviously doing something right," says Finlayson. "I was very conscious that a lot of people coming to see us had only ever danced in clubs before, and it was definitely that kind of groove-based approach we were after, yet we never really discussed it in those terms: we just played. It was two years before we had a rehearsal, and then only because we were due to be making the first album."

This initial imposition of studio discipline proved to be a vital catalyst. "It forced us to impose at least an element of structure," Finlayson continues. "And that led to the realisation that we could experiment and improvise all we liked, get away with all kinds of nonsense, as long as we built in a few islands of sanity amid the chaos, to reassure the audience that we knew what we were doing. Which is pretty much how we've carried on, really."

That 1994 debut, Venus in Tweeds, issued by the Scottish folk independent Greentrax, remains the label's all-time bestseller. It's been followed by three more albums (four, if you count an early RealWorld live CD), most recently The Arms Dealer's Daughter, released under the band's own Shoogle Records imprint.

It follows a bumpy period in their career, with mounting personal and interpersonal tensions eventually leading to MacLeod's and Ivitsky's departure in 2001. After a full decade with the same personnel, and given the calibre and character of the players involved, finding suitable replacements wasn't looking hopeful - but then in stepped MacArthur, another longtime stalwart of Edinburgh's close-knit roots scene, who'd already deputised on bass a few times. Plumb, meanwhile, was serendipitously discovered busking at the market in Hobart, while Ivitsky was on honeymoon there.

The 22-year-old self-taught prodigy learned virtually the band's entire repertoire from CDs and downloads in record-breaking time, ready to join them when they flew in for the Tasmanian leg of their tour. "We'd been thinking he'd maybe do two or three numbers with us," remembers Crosbie, "but he came on right at the start, and played the whole gig. Anything he wasn't quite sure of, he just jammed - and it all sounded fantastic." Besides his phenomenal playing on The Arms Dealer's Daughter, Plumb also wrote more than half of its all-original material.

The new record's sparkling melodies, killer rhythms and buoyant cosmopolitanism vividly reflect the mood of a band enjoying a fresh lease of enthusiasm. "It's nice to be learning again," says Crosbie. "When you play with the same people for ages, you tend to know the type of thing they're likely to do, and vice versa. Having new people in the band makes it more exciting."

"Ten years without a single line-up change is a very long time," Finlayson points out. "And this is a band built on very strong personalities, intense relationships and lots of creative friction. It's never going to be all sweetness and light - although it is pretty close right now."