Twenty years on, it is Altan's ability to incorporate the new into the traditional that allows them to cross musical and geographical borders and has guaranteed their longevity, writes Siobhán Long.

The irony isn't lost on Mairéad Ní Mhaonaigh or her co-conspirators in Altan. As their light shines ever brighter on the world music stage, they've chosen to christen their 10th album in 20 years Local Ground.

Two decades criss-crossing the globe have inevitably left their mark on the band, but Donegal still breathes fresh life into their veins. And it's this local identity that both sets them apart from and unites them with an eclectic mix of musicians internationally, all of whom bring their own folk music to a world stage. Having performed within the last 12 months in the US, Korea, Japan, China, France, Spain, Portugal, Italy, Denmark, Sweden, Holland, Belgium and the UK, Altan have expended far more energy engaging with audiences far removed from our conventional notions of "traditional" than holed up in céilí houses around Ireland.

"We are as much a world music band as a traditional band," Ní Mhaonaigh insists. "We bring our music, Irish music, to a world stage, where we are perceived as world musicians. We are influenced by the music of today, and we bring that subconsciously into the music. I feel that although we are playing traditional music, we're bringing ourselves to that old music. The older musicians who taught us the songs and the tunes had their influences and we have ours."

Mark Kelly, one of Altan's two guitarists, who shares touring responsibilities with his American-based counterpart, Dáithí Sproule, is quick to put a finger on the essential pulse that fires traditional music in the 21st century.

"Altan has always shown deference for where the music came from on the one hand," he suggests, "but we've always adopted a modern approach in terms of the rhythms and the harmonies. Traditional music has a huge resonance and relevance for me today. I feel it's very much part of where I'm from and who I am today. At a time when we're seeing enormous changes in society - this is a much more multi-cultural society than it was 10 years ago - my sense of identity is influenced as much by the music as it is by listening to U2, by watching Liverpool winning the Champions League, and so on. I was lucky enough to come across this music, and the language, and they've informed some of the choices I've made. My son is going to a gaelscoil now, and I'm not sure that that would have happened if I hadn't had that part of who I am opened out."

Dáithí Sproule sees the very "local" nature of Altan's music as the key to understanding its appeal to a world music audience. "The really strange thing is that by being really particular, like we are," he offers, "focusing on traditional Irish music and with an emphasis on Donegal music, and by delving into that as deeply as we can, we come up with something that really hits home to people all around the world. It hits home on a very deep level because it is so particular, so 'local'. It is music that has been rooted in a particular place and has been nurtured and worked at and enjoyed by particular communities rooted in a certain patch of country, and because of that it belongs, and people in Dallas and Tokyo, who might have lost that sense of deep belonging, feel it and are moved by it."

Altan's insistence on making the music their own whispers of a willingness to get beneath the skin of it, and not to treat it with the preciousness that some commentators consider is a necessary part of the preservation process. Traditional music can't thrive in aspic, Ní Mhaonaigh insists.

"You can't put it into a glass cage if you want it to be vibrant," she says. "If it's in a vacuum, it won't develop. It's something we do very carefully, of course, but not self-consciously, because we have to enjoy what we're doing too." Mark Kelly sees the essence of the music as having a raucous quality, a life force that propels it beyond conventional notions of traditional music. Without that verve, he suggests, the music simply wouldn't appeal to him as a musician, or to listeners.

"I remember Frankie Kennedy (Altan's founding member and flute player, who died of cancer in 1994), was always into rough music that had energy," Kelly recounts.

"He liked blues, and at that time I would have been listening to the likes of Steely Dan, who would have been very refined, I suppose. But between those two extremes, there's a friction and a dynamic that keeps the music alive. That energy is completely natural to traditional musicians, and there are classical musicians who aspire, after years of training, to be able to interpret and express in a way that's completely natural, as traditional musicians do."

"It's when you have the soft and the hard together, the yin and the yang, it brings something primal to the music," Mairéad adds. "Anyone can sit down and read a series of notes. I think we're interpreters. We play the tunes we heard when we were growing up from John Doherty, Con Cassidy or Dinny McLaughlin, but we have to bring ourselves into the music too, and that's the catalyst that brings the music to another level."

One of the reasons traditional music might not be considered relevant by younger listeners is its fondness for adopting an apparently apolitical stance in its songs.

While tales of love lost, thwarted and triumphant abound, few writers take specific political perspectives - aside, of course, from the unapologetic politicking of rebel songs that occupies a place apart from traditional music.

Mairéad Ní Mhaonaigh vehemently disagrees with any suggestion that Altan's music is apolitical. "Frankie always said that the strongest thing we can talk about is love," she says. "He was a political science student, and he held strong views on Northern politics, but what Altan want to do is reflect the core of Irish society. We don't make political statements, but we sing our songs that came from all our people. It's too complex to say 'up this' or to put any one group down. We meet everybody from every persuasion wherever we go, and this is music of integration, not of division."

Altan's forthcoming Bloomsday concert is a sort of a homecoming, Mairéad suggests. Joyce's unashamed bawdiness, his glory in language is, she insists, rooted in a first-hand acquaintance with Irish, which captures the nuance and gesture of human relationships with far more precision than the queen's English.

"James Joyce's English was based on the rhythm of the Irish language," she says. "He wrote things that shocked English language speakers, but he was thinking in Gaelic. I've sung songs that, if they were in English, would have been banned too. The psyche of the Irish language is completely different to the English-speaking world. James Joyce spoke of the 'snot green sea', directly taken from the Irish language, and that's what we're about too."

Is some of Altan's work lost in translation then? Ní Mhaonaigh thinks not: "Our music has all the aspects of all the emotions that we all need to understand," she says. "It speaks at the softest and at the same time the most raucous level. I would hate to be perceived as a musician who's keeping a light alive. To me it's as important as any other music in this world. Why bother playing it for any other reason?"

Altan play a Bloomsday concert in Vicar St on June 16th, alongside Dermot Dunne and Ariel Hernandez on accordion and guitar and sean nós dancer Seosamh Ó Neachtain. Tickets cost €22, or €80 for a table of four, are available from the Improvised Music Company: 01-6703885 or Ticketmaster: 0818-719300; www.ticketmaster.ie (booking fee applies).

Altan's latest CD, Local Ground, is out now. www.altan.ie