NO drums, no clog dancing. If you require an idea of what to expect when The Unthanks play Edinburgh's Queen's Hall next week that's as good a summary as any.

"This may be the first tour that doesn't have clogs," laughs Rachel Unthank. "I might have to wear them just to make me feel at home."

Today fog is covering Northumberland but Unthank is all spark and sunshine in a Geordie accent. We are here to talk about the latest Unthanks tour in support of a soon-come new album that sees them take one of their regular detours into the work of other artists.

Loading article content

The family-flavoured folk band has always been open to incorporating new sounds and textures into its sonic identity. More than that, though, The Unthanks have also issued three albums in which they have covered the songs of Robert Wyatt and Anthony and the Johnsons, collaborated with the Brighouse and Rastrick Brass Band and even ventured into the songbook of the shipyards.

Now, as a follow-up to the lushness of their last Unthanks album proper, Mount the Air, which last year won the band the Radio 2 Folk Awards best album category, they are returning with their next Diversions album. Volume 4 sees the band – which includes Unthank, her sister Becky and husband Adrian McNally – cover the songs of Molly Drake. And who is Molly Drake? Well, she's Nick Drake's mother.

The Unthanks have long been fans of Nick Drake, one of music's little boys lost. Indeed, you can hear Becky cover his song River Man on the band's first album Cruel Sister in 2005 (back when they were still operating under the name Rachel Unthank and the Winterset).

But now they have turned their voices and musical skills to Drake's mother's work. And if Drake's songs were little known for decades after they were recorded back at the start of the 1970s before advertisers and Brad Pitt started noticing them, his mother's songs are even more obscure.

Deliberately so. Recorded on a ferrograph in her home in the 1950s by her husband, a keen sound recordist, they were never meant for public consumption. They only really came to the public notice in 2013 when the Drake estate finally approved an album release of the crackly recordings that revealed that it wasn't only her son who could deal in minor-key melancholia.

Now the Unthanks are offering us their own version of the motherlode. "She is an extremely interesting songwriter," suggests Unthank, "really emotional and philosophical and witty and thoughtful."

"When we listened to that album I suppose it was interesting to hear where Nick may have got his ideas and thoughts from in his background. But, actually, Molly's an artist in her own right and we really connected with her straight away because the melodies are so beautiful and she doesn't shy away from the dark side, which is something we are drawn to in our music as well."

Every life has its darkness of course. Molly Drake was an upper-middle class housewife who continued to write songs and poetry up until her death in 1993, almost two decades after she discovered her son dead in his bedroom having taken – who knows how deliberately? – a fatal dose of Trypitzol.

"She was such an interesting lady," argues Unthank. "She and her husband Rodney lived in the Far East before the war and when the Japanese attacked Burma she had to walk out of the country through really difficult, dangerous, mountainous terrain. Lots of people died trying to escape. And she left her husband behind not knowing when she'd see him again."

As in life so in art, Unthank reckons. "There's a strength that comes through in her music and in her writing."

How that will translate into the world of the Unthanks remains to be seen. When we speak there are no sneak previews of the new album available but Unthank says to expect lots of harmonies, piano, fiddle, bass and clarinet. Oh, and Drake's poetry will be woven into the mix as read by her daughter Gabrielle.

What do these Diversions albums represent for The Unthanks? A chance for the band to be musically curious, Rachel Unthank suggests. There may be another one later this year that draws on the band's recent work with orchestras.

It's tempting to see parallels between the way biography and music are intertwined in the Drake family story and that of the Unthanks. But then for Unthank life and music has always been entwined.

She grew up the daughter of George Unthank, a member of rowdy Northumbrian folksters The Keelers, and she Becky grew up in harmony. "Singing has always been a big part of our relationship. When I went to university in Glasgow we used to sing on the phone. There's seven-and-a-half years between us so she was still quite young when I left home. But singing was something we used as communication. She would come up to Glasgow and we would have a weekend singing.

"We feel really lucky. It means wherever we go we've got each other still and it's a thing we can share. And, by extension, Adrian and the rest of the Unthanks feel a bit like a rolling family band."

Unthank came to Glasgow in 1996 and stayed here four years studying theatre and history. "I'm from a village near Newcastle and Newcastle is a great city, but it's quite small, so to come to Glasgow was a big adventure. I really wanted to live in a big city and when I came to Glasgow I just knew it was the city for me. There was so much going on.

"I didn't have loads of money so I couldn't really afford to do very much, but I had an amazing time. I spent most of my time when I should have been revising going to Celtic Connections."

You wonder, growing up in a folk family, if there was ever a desire to rebel, to pin her colours to another sound? "When I was a teenager I was totally into grunge," Unthank admits. "Nirvana and Pearl Jam. I liked to dress in that way as well because I was 15. But I also went to folk festivals and still listened to folk songs and went to ceilidhs and still went clog dancing on a Friday night.

"It was a way of life for our family. We loved going to folk festivals. It was fun, so to have rebelled completely would have meant I couldn't take part in the things that I loved. So I had my little rebellion but it was alongside … As well as."

Hmm, I tell her, I can see Diversions volume six being The Unthanks covering Nirvana. "Yeah," she says, sounding a tad unconvinced. "Becky still gets horrified. She wasn't quite as into rock as me."

That said, as Unthank points out, these days the band's music is likely to turn up on the same programmes as Nirvana on 6 Music. Folk is no longer a scene apart .

"We're not just played on The Folk Show… That's a great thing, to be played on The Folk Show but now there's an openness for music lovers to listen to lots of different kinds of music. We don't just listen to folk. It's exciting and interesting for us to be seen in that world rather than just straight folk. That's lovely."

The it is time to go. The fog is already burning off.

The Unthanks play Edinburgh's Queen's Hall tomorrow. Diversions Vol. 4: How Wild The Wind Blows – The Unthanks Perform The Songs & Poems Of Molly Drake is released on May 26.