It's hardly surprising that the career of folk singer and songwriter Beverley Martyn tends to be defined through her associations with some of the most exalted names in roots music.

She was, after all, the teenage girlfriend of both Bert Jansch and Paul Simon, a close friend of Nick Drake, the wife of the late Scottish singer and guitarist John Martyn, and recorded with the likes of Levon Helm, Donovan and Sandy Denny.

Such is the pedigree of Martyn's collaborators it's easy to forget her own achievements: she signed to Deram as a solo artist in 1966, performed at the Monterey Pop Festival in 1967, and wrote, played and sang with her former husband on Stormbringer! and The Road To Ruin, two terrific albums released in 1970 on Island Records. Contemporaries such as Linda Thompson, Vashti Bunyan and Anne Briggs may now be getting due recognition, but Martyn remains under-rated as an artist in her own right.

That may yet change. Restored to health after a period of illness, at the age of 66 Martyn is returning with a fine new album in the autumn, entitled The Phoenix and the Turtle, and is playing a short run of dates next week as part of the Edinburgh Fringe. Recorded over the past couple of years with Mark Pavey, who has previously worked closely with another of her old acquaintances, the tempestuous guitarist Davy Graham, the album includes a cover of Memphis Minnie's venerable blues standard When the Levee Breaks. It's a song Martyn has been singing "since I was about 15 and playing with my old jug band, The Levee Breakers, although unfortunately I'm now the only living member left."

It also features new original material, including Reckless Jane, a song she started writing with Nick Drake shortly before his death in 1974. "When John and I lived in Hampstead Nick lived one stop down the tube line, and he would come around and babysit sometimes," she says.

"John liked Nick, he was very gentle around him. Nick was no threat, so John sort of looked after him. We started writing Reckless Jane one day as a bit of a joke. I couldn't look at it for a long time after he died, I couldn't deal with anything to do with Nick, but then finally I decided to finish it." For the album Martyn has recorded it in the classic Drake style, with a string arrangement in the tradition of the late, great Robert Kirby.

However vibrant her current activities, Martyn struggles to shake off the shadows of the past. Her recent memoir, Sweet Honesty, recounts a life filled with more than its fair share of trouble, particularly during her marriage to the volatile John Martyn.

Though they were together for over a decade, their musical partnership was relatively brief. After The Road to Ruin was released in late 1970 her husband became fixated on a solo career and, although Martyn made some contributions to his solo work, her music-making all but ceased as she raised their children and increasingly fell prey to his drinking, drugging and violent mood swings, before she finally left in 1979.

At times she thought she would never escape alive, but writing the book, and John's death in 2009, have made her more philosophical. "It was good, it was bad, and sometimes it was magical," she says of the marriage.

"There was love there - it was the drink and the bad drugs, the very heavy ones, that changed his disposition, and they made life unbearable for anyone around him.

"We had children and I was the one who had to be together, whereas he was wild, he lived on the edge. He loved excitement and he had far more bottle than me. He had a lot of guts, and strong belief in himself, but he couldn't stop the drink, and I wouldn't stay with a man who was killing himself."

John Martyn's 1980 album Grace and Danger is marinated in the misery of their divorce. It was his last great work, followed by a rapid decline in his songwriting and, eventually, his health. "Well, that's what happens, you feed off people," she says. "Was I the muse, who knows? But we would play together a lot in the evenings when the kids were in bed, and I think he missed that vibe."

Martyn's mixed memories of the defining relationship of her life have not tainted her appreciation of the music the pair made together. She promises her upcoming concerts will feature songs such as Auntie Aviator and Primrose Hill from those two records, as well as material from her new album.

"I have a really good feeling about it," she says. "I'm very proud to be still be here and making music."

Beverley Martyn plays the Acoustic Music Centre at St Bride's, Edinburgh, August 5-7.