It began as a social circle and now it's a semi-circle of fiddlers onstage.

Meet Rant, one of the concert attractions at Fiddle 2012, the latest instalment of the annual bowing bonanza that fills a corner of Edinburgh to bursting point with fiddlers of all ages and levels of playing ability.

When a group of Scotland's foremost fiddling talents met up at another fiddling spree, the Niel Gow Festival in Dunkeld last year, it was a reunion of four friends who were there to play independently.

Sisters Jenna and Bethany Reid, from Shetland, and Highlanders Sarah-Jane Summers, from Inverness, and Lauren MacColl, from the Black Isle, have known each other for years and it was inevitable that, if they were gathered together in the same room, music would break out.

"It was never our intention to play gigs," says MacColl, whose new album with flautist Calum Stewart, Wooden Flute & Fiddle, is currently attracting enthusiastic reviews. "We just thought it would be fun to have a tune and a rant about what was going on in our lives. It was a social thing but then, when we played together there was a certain resonance in the way our styles and sounds merged together and it began to sound interesting."

Part of their reluctance to form a working partnership was due to their awareness of the already plentiful supply of fiddle bands with three, four or more fiddles in the front line. Jenna Reid plays with one of the leading examples, Blazin' Fiddles, and with others such as Shetland's Fiddlers' Bid and Highlanders Session A9 at home, as well as Donegal's Fidil, fellow Fiddle 2012 guests Celtic Fiddle Festival and more recent, likewise popular arrivals, the Nordic Fiddlers Bloc, festival organisers are spoiled for choice.

"We didn't think there was room for more of the same," says MacColl. "But we did quite quickly develop our own approach. We decided early on we weren't going to involve a rhythm section, so that would make us different from some of these groups, and whereas others, like Fidil, for example, quite often use the fiddle as a rhythmical accompanying instrument, we were keen to just use the resonance of the fiddles and to try to create interesting harmonies."

Early feedback suggested that while their name indicated an unfettered, going-for-it style, the reality was more of a chamber music approach.

"You have two Shetlanders and two Highlanders, plus Sarah-Jane has been based in Oslo for three years, so there's a Scandinavian influence to accommodate too, and it was quite a challenge to come up with arrangements that gathered all that together without having a guitar or piano," says MacColl. "But what gives us something else that's different from other fiddle groups is the fact that we're four girls, so there's more of a feminine touch. We're maybe more gentle, although we all like to let it rip on fast tunes, too."

Being based in Norway, Summers has added the Hardanger fiddle, with its resonating strings and in-built harmonic potential, to her repertoire and the tunes that are part of that instrument's tradition can present difficulties in transferring them to the conventional fiddle. A more physical problem, with the four pals now either living hundreds of miles apart or travelling separately on other assignments, however, is getting everyone together for rehearsals and to work up new material.

"We've managed to avoid Skype conferences so far," says MacColl. "I can see how that works for some musicians and it would be easy in some ways for Jenna, Bethany and myself to get together in Scotland and let Sarah-Jane add her parts later. But the point about the way we play is that it's about having four people in the room at the same time. It's a four-way dialogue and we all play equal parts: there's no designated soloist; we all take turns at playing the melody and all accompany each other."

The point about all being in the same room at the same time extends to concert presentation. Ideally, Rant would work without microphones or pick-ups and let the natural sounds of their fiddles reach their audience, although on larger festival stages this isn't always possible. For Fiddle 2012, where they're sharing the concert billing with the brilliant Chicago-based Irish-American fiddler and prolific composer Liz Carroll, they're hoping to get by with minimum amplification.

"The first gig we played was totally acoustic in a church in Cromarty and it worked perfectly," says MacColl. "We're not at the recording stage yet but that church would be the ideal location."

Rant and Liz Carroll play the Queen's Hall, Edinburgh, on Saturday. Fiddle 2012 runs from tonight to Sunday. Visit www.scotsfiddlefestival.com