Joan Baez is still passionate about causes close to her heart

At 70, Joan Baez is still campaigning and singing about the causes that have influenced her music since the 1960s.

Joan Baez in concert in Marseille.

The first sight of Joan Baez, in a concert hall in the Mediterranean port of Marseille during her recent European tour, was disconcerting. Here, at first glance, was a stiff, hobbling woman of advancing years.

But there was a reason for the limp and painful gait: Baez had barely recovered from a heavy fall from the treehouse to which she often retreats, for reflection or to sleep, in the garden of her Californian home.

And in the 90 minutes that followed her stage entry, she presented compelling evidence that while she may indeed have passed 70 this year, there was nothing remotely frail or doddery about her performing skills, stagecraft or wit.

The brightest female star of the 1960s American folk and protest movement still possesses enough of that distinctive, instantly captivating soprano to hold large audiences in her thrall.

Some of the causes she embraced half a century ago - a resolute opposition to discrimination, much of American foreign policy and repression generally - still matter to her and inspire her work. Environmental issues have become increasingly important to her, and that is reflected in her songs. And in Marseille, mindful of the city's large Tunisian community, she dedicated a song in Arabic, Jari ya Hammouda, to their compatriots' uprising.

Her injury has failed to weaken her stamina for punishing tour schedules. The night before Marseille she had been in the south-western city of Toulouse; there was a day off before Grenoble in the foothills of the Alps and then it was back west to the Massif Central, with dates in the Netherlands and Scandinavia to come. "It was a bit of a mess," she tells her Marseille audience, patting her stomach, "But it's nearly healed."

The voice may not be quite what it was when Baez proved instrumental in bringing to a wider public the songs of Bob Dylan, whose own 70th birthday on May 24 came four-and-a-half months after hers.

But with a little readjustment in arranging her songs, she hits the notes she needs, keeps the guitar accompaniment simple and - unlike Dylan - engages effortlessly with her listeners.

The continuing commitment to human rights appears to present a stark contrast with the more commercial route chosen by Dylan. Baez's old collaborator, soulmate and romantic partner found himself having to justify accepting dates in China without mention of Beijing's treatment of dissidents. There were also allegations that his songlist was censored, though Dylan denied this.

The 70 years of Joan Chandos Baez have produced about half as many albums and half a century of relentless social activism.

She is the daughter of a Mexican-American physicist, who died in 2007, and a Scottish-born mother, who is still alive.

After narrowly graduating from high school, Baez studied drama and sang in the coffee houses of Boston and Cambridge, Massachusetts, making a significant breakthrough when she appeared unbilled at the 1959 Newport folk festival.

Although folk, including the traditional ballads from her mother's native land, was considered her genre, she enjoyed serious chart success with early albums and drifted to other musical forms including country, gospel and pop.

Her own songwriting exploits have been respectable rather than spectacular. While her 1975 composition Diamonds and Rust won notable acclaim, she is more readily associated with interpretations of the songs of others.

Some regard her covers of early Dylan jewels, including Don't Think Twice, It's All Right, Farewell Angelina and the powerful account of the aftermath of nuclear warfare, A Hard Rain's A-Gonna Fall, as the classic versions of his work.

Her music and campaigning brought her derision from the American right, but also a fistful of honours, most recently this year from Amnesty International, which initiated what will become the annual Joan Baez award for "outstanding, inspirational service in the global fight for human rights".

Back in the 1960s, some were ready to dismiss folk music as a tool of communism. One prominent US right-winger, Dr Fred Schwarz, championed a conservative equivalent, Janet Greene, reportedly telling her: "They have Joan Baez, who do we have?"

But Baez's charisma made her a tough opponent. She marched shoulder to shoulder with Martin Luther King; visited Hanoi to distribute mail and Christmas presents to American prisoners-of-war even as US forces bombed the city; joined peace demonstrations in Northern Ireland; supported dissident Czech musicians jailed in Communist Czechoslovakia and stood in vigil outside US jails when criminals were executed.

With so many causes dear to her heart, it is hardly surprising that Baez soundbites are easy to find. "I've never had a humble opinion," she once said. "If you've got an opinion, why be humble about it?"

And there is no sign, not yet at any rate, that she intends to slow down, grow older gracefully. From June 23 to the end of July, she appears on stage in San Francisco as part of Teatro ZinZanni, a production promising "European cabaret and cirque, divas and madmen". Later in the year she tours again in North American and France.

All, she might say, in keeping with another of her guiding principles: "You don't get to choose how you are going to die or when. You can only decide how you're going to live."