Joan Baez had to grow up in public. At the age of 18, she played in front of 10,000 people at the Newport Folk Festival. Her first studio album sold more copies than any other female folk singer in history. At 21, she was on the front cover of Time magazine.

She released her latest album ‘Whistle Down the Wind’ last month. It’s full of wonderful covers that evoke the range and scope of her output of that era. There are protest songs (‘Civil War’ and ‘The President Sang Amazing Grace’) and forceful attacks on the corruption of American politics, recalling her appearances in front of massed crowds at the demonstrations in Selma and Birmingham in the sixties.

Her early repertoire was a product of the interwoven folk traditions of England, Scotland and America – she sang familiar Child Ballads like Mary Hamilton, Geordie and The Water is Wide, and songs that had been popularised by Woody Guthrie and Pete Seeger, like Pretty Boy Floyd. This was the common reservoir from which the musicians that we generally consider part of the ‘American folk revival’ movement drew. From her new album, ‘Silver Blade’ is a classic ballad about thwarted romance and revenge in that style.

Some folk singers deliver the material pretty straight: the English folk singer Anne Briggs, for example. But Joan completely made those old songs her own. With her strange and other-worldly voice, she re-animated these fragments of an older world, with extraordinary, elemental beauty. And in that sense her voice encapsulates the ultimate value of folk tradition – a value that is much more radical than the picture portrayed in films that pay tribute to it.

The folk singer protagonist of the Coen Brothers’ tribute to the revival era ‘Inside Llewyn Davis’ says: “If it was never new, and it never gets old, then it’s a folk song.” The mythology of folk tradition tries to provide a sense of continuity between the oral traditions of yore and the present day – a conversation over time in which stories are told, passed on, retold and passed on again.

It’s the well-known image of the eternal troubadour, unbound by circumstance or place, his freedom his song and the open road. Bob Dylan self-consciously adopted that attitude towards folk traditions. In his ‘Chronicles’, a semi-fictionalised account of his early career, he writes: “I really was never any more than what I was—a folk musician who gazed into the grey mist with tear-blinded eyes and made up songs that floated in a luminous haze.”

But Dylan is well aware that that’s not quite true. Modern folk addresses itself self-consciously to lost worlds – the Jacobite wars, the American Civil War, ballads and love songs and stories of a different time, things that must be ‘revived’. That is the pleasure and pain of being a folk enthusiast – to know that these songs bear the mark of discontinuity between the pre-modern past and modern life. Dylan himself spent hours in the New York Public Library poring over old newspapers from the mid-nineteenth century. He wanted to escape the present. He found the modern world too painful, too mad.

That friction between the dull present and the romance of an imagined past is what gives folk its energy and power – a thing that has to feel lost to be rediscovered. Every new articulation of an old song bears the fresh imprint of its own time, and that’s what makes it interesting.

Dylan’s voice hovers in the background behind Baez’s cover of Josh Ritter’s ‘Be of Good Heart’. “I hear the wild dog in the dark” recalls Dylan’s masterpiece ‘One Too Many Mornings’: “Down the street the dogs are barkin’/And the day is a-getting’ dark.” And the tone of his song of unrequited love ‘Don’t think twice it’s all right’ is echoed too: “I don’t know nothing ‘bout where you’re goin / that don’t mean a thing to me.” And “It ain’t no use to sit and wonder why, babe, it don’t matter, anyhow.”

Dylan and Baez shared a brief relationship which ended in acrimony. In 2009, Dylan apologised for how badly he had treated her: “I feel very bad about it. I was sorry to see our relationship end.” Baez consciously brings those songs and that experience into a performance of exquisite sadness. Her voice cracks and frays over the lines: “And I know that I just may / Have been a way to pass your time / Just a stop along your way / as you were a stop on mine.”

She does the same in ‘Another World’, a cover of a song written by the singer Anohni. In her hands, Anohni’s soupy texture backed by a piano is stripped off and replaced by a rhythmic Velvet-Undergound-style surf beat. It’s a move that pays off – Anohni’s creation is poetic, mysterious yet strangely anodyne. Baez gives it power and urgency, lending it the tone of an Old Testament Jeremiad.

Joan Didion, the American essayist, reflects: “Joan Baez was a personality before she was entirely a person and, like anyone to whom that happens, she is in a sense the hapless victim of what others have seen in her, written about her, wanted her to be and not to be … above all she is the girl who ‘feels’ things, who has hung on to the freshness and pain of adolescence, the girl ever wounded, ever young.”

For many fans, their image of Baez will always be set in aspic – ever wounded, ever young. But Baez has shown that she is much more than that. She once said: “The easiest kind of relationship for me is with ten thousand people. The hardest is with one.” It is that spirit that gives ‘Whistle Down the Wind’ its complexity – a fascinating portrait of a woman grappling with the loss of love, growing old and political pessimism.