Sarah Lee Guthrie - grand-daughter of Woodie - is still coming to terms with her legacy, she tells Siobhán Long

Humdinger songwriters aren't made, or so the story goes. They emerge from the womb, perfectly formed. Sarah Lee Guthrie is the kind of singer-songwriter who might not advertise her lineage, but her high octane songwriting reeks of an inheritance that stretches well beyond her twentysomething years on the planet.

So let's get the family tree questions out of the way first, since even Sarah Lee is prepared to admit that having a grandfather by the name of Woody, and a father by the name of Arlo, may have opened a few doors along the way.

Having a grandfather who is widely regarded as the grand-daddy of American folk music might prove at the very least intimidating. Sarah Lee insists she's still getting to grips with the enormity of Woody Guthrie's legacy.

"I think that my awareness of Woody has grown as I've gotten older," she offers with an unexpected tentativeness, "and to be honest I've learned much more about him and his legacy since I started playing music myself, because I'm around all those people who were influenced by him.

"It wasn't that way when I was growing up though. My dad was on the road and I never took it upon myself to go listen to the records. It was there but it wasn't something I spent any time thinking about, until I started playing music."

Sarah Lee's father, Arlo, was no slouch himself when it came to matters musical. The eldest son of Woody, he found himself occupying pole position in the folk firmament for a few years following the release of his seminal album and song, Alice's Restaurant, in 1967.

"My dad has been a huge influence on me," she acknowledges. "He was the first person I ever played with, but that was just part of what happened to all our family as we were growing up. His real influence on me, musically, happened when I tour-managed him back in 1997. Performing with him was an amazing learning experience, watching someone who has been doing it for so long and doing it with the greatest of the great. He taught me too how to deal with the legacy that's on our shoulders.

"He made it very easy for me, being the granddaughter of Woody and the daughter of Arlo, simply by setting an example. And he taught me how to step out into my own music and my own world. I bring all of that with me - from him."

Sarah Lee Guthrie and her husband Johnny Irion's recent joint recording debut, Exploration, reveals a couple whose musical and romantic lives are entwined in the same way that Gillian Welch and David Rawlings are.

Often compared to Emmylou Harris and Gram Parsons, and at times even to Johnny Cash and June Carter, Guthrie and Irion's alliance is a far less tortured beast, shot through with an inherent optimism rarely found lurking in the depths of country music.

Surprisingly, the old assumption that artists are at their creative best when their personal lives are at their most unhappy is brought to its knees by the Guthrie/Irion collaboration. For them, personal happiness has multiplied rather than divided their creative energies.

"As artists we laugh about this," she admits. "We've thought, 'why don't we break up so that we can write better songs?'. But I take a lot of pride in the songs that we write. When we first got married we thought we could take on the world, and we want to show people how that can be done, how to be happy and still write good songs. I'm an optimist by nature and that's how I'd like to keep things."

With three of the 12 songs written jointly by Sarah Lee and Johnny, and two more of her own compositions on the album - Mornin's Over and the Hoyt Axton-inspired Holdin' Back - Guthrie has been busily honing her ability to marry words with music, having long considered herself to be more of a poet than a songwriter.

"I am more of a poet," she says. "I can sit down and write but not necessarily in a song. I sometimes write pages and pages and finally come up with something that might become a song. I'm definitely pressured to write songs and I'm always looking for a song but it's not easy for me. I really am a writer, whereas Johnny is a song crafter. That is what he does and he does it constantly and he does it well. It doesn't come as naturally for me as it does for him, but then again at times he's lost for words and I have plenty of words."

Johnny Irion's Columbia, South Carolina, roots have lured the couple back home recently where they find the space to write in between their road trips.

He has little difficulty finding the motivation to write at a time when the US is shaking its fist at everyone in sight, both at home and abroad.

"More is more and more is better. That's all we seem to hear these days," Irion says, with a barely suppressed anger. "It pisses me off but I've been writing more love songs than political songs lately just because I need a break. The fact is, where we're at in America right now, so many people just don't want to hear political songs. The way I see it, there's no clear right and wrong, but if we all could just get together we could work it out. As long as everybody has a point of view, we're okay, but if there's only one point of view being aired, that's bad news for everyone."

Sarah Lee Guthrie and Johnny Irion play Whelan's tomorrow; Cuba in Galway on Thurs; Grant's Hotel in Roscrea on Fri. Exploration is out now on New West Records