Her half-brother is Pete Seeger, the venerated US folk icon who influenced Bob Dylan and Bruce Springsteen, while for more than 30 years she was the partner, and later wife, of Britain's great folk custodian, the socialist singer, songwriter and radical playwright Ewan MacColl.
MacColl wrote The First Time Ever I Saw Your Face for her, a song which became a global hit for soul singer Roberta Flack and is now a standard, sung by everyone from Johnny Cash to George Michael. At the time Seeger was a young banjo player, still in her early 20s. Not long arrived in Britain from her native New York, she had quickly stolen the heart of MacColl, a man twice her age who was married to his second wife Jean Newlove, mother of Kirsty MacColl.
That was over half a century ago, but at 77 there is nothing remotely weathered or nostalgic about Seeger. Her brisk conversational style suggests she doesn't suffer fools gladly, if at all. Her late husband possessed a similarly no-nonsense demeanour, as well as being famously intransigent when it came to preserving what he regarded as the purity and integrity of folk music.
All of which makes Seeger's latest project, Folksploitation, the more surprising. It's a mini-album by Broadcaster, aka Lewis Atkinson, a DJ and electronic musician who previously gave a thoroughly 21st century overhaul to the original 1960s BBC Radio Ballads, in which both Seeger and MacColl had been involved. This time Broadcaster asked Seeger to record 52 new vocal tracks. He eventually selected seven, adding modern textures, hard electronic beats and dub, trance, rave and hip-hop rhythms.
What on earth would MacColl have made of this blasphemous meeting of traditional folk and rude modernity? Seeger laughs. "A few people have asked me that. I think once it's not passed off as folk music then that's fine. Look at the title of the record. It's doing something different, something composers have done for generations, which is to use folk music as an embryonic source."
Seeger became involved in the project via her son Calum, who produces Broadcaster. She acknowledges a quietly crusading agenda; part of the impetus for taking part was her realisation that "if nobody sings these songs they don't get passed on". The First Time Ever I Saw Your Face is universally recognised, but none of the other six North American folk songs on Folksploitation are particularly well known in Britain. "It's the act of singing such songs and the act of giving them respect and continuity that's most important right now," she says. "I don't think Folksploitation will being people to folk music, but it might bring them to my concerts, at which point they won't know what's hit them. If they come expecting Folksploitation they won't get it, they will get something entirely different."
And they are coming, both to Seeger's concerts and to folk music in general. She suggests that more and more people are "fleeing from a lot of the music that you hear constantly, whether in an Indian restaurant or on a train. The basic human right to listen to what you want to listen to has been abrogated totally in our society. There is so much music that you are forced to listen to at decibels that are almost impossible for the ears. People are looking for a more modest type of music, one that's more community minded. Popular music is somewhat orgiastic, but folk song comes from a different place. It wasn't made in order to turn a profit or to make somebody famous. It expresses some aspect of the community from which it sprang."
This sense of making music that walks hand in hand with community and society has always been at the heart of Seeger's career. "The thing I like especially about Folksploitation," she says, "is that each track makes a point: war, abortion, love ..." She was blacklisted from the United States in the 1950s for her avowedly left-wing stance, which included embarking on visits to Russia and China, and she subsequently spent a 30-year exile in Europe. After the death of MacColl in 1989 and a gradual softening of anti-Communist attitudes back home, Seeger returned to live in the US in 1994, writing, performing and teaching songwriting at Northeastern University in Boston. She loved it, but came back to Britain two years ago. Why? "Family. The country. I have a history here, I lived here a long time. I certainly didn't come here for the weather, although when the sun shines the British Isles are heaven."
She remains politically engaged, but concedes that these days the "targets are more difficult. Some of them are socially unacceptable: the destructive elements of religion, or overpopulation. You can't really talk about these things without feeling anti-religious or anti-baby, but the world is at a huge tipping point. It's very different from writing a song about Margaret Thatcher or David Cameron or fascism. People know this stuff but they don't want to see it or hear it, they want to come to a concert to enjoy themselves. So you have to make a nice, happy chorus about saving the earth."
In her late 70s, Seeger has lost none of her verve for singing or performing. "I love hearing my audience sing together and watching them light up," she says. "It's quite wonderful, particularly seeing increasing numbers of young people coming to my concerts. Their grannies, or their great-grannies, will have brought them, saying, 'I saw Peggy Seeger when I was five.' And I'm still around! When they come, for the most part they stay and so often they go out with their eyes shining." She sounds surprised. "I'm not surprised," she says imperiously, "but I want you to be surprised."
Peggy Seeger plays Carnegie Hall, Dunfermline, tomorrow; the Tolbooth, Stirling, on Friday; and Milngavie Folk Club on Saturday.