In a very real sense all in modern popular music are Pete Seeger's children, as the fanzine writer Jon Pankake once pointed out.

And not merely those who got themselves a five-string banjo, lengthened the neck as Pete advised, and worked hard to get the audience to sing along with some folk song picked up from Africa, Indonesia or Middle America.

Eclectically cosmopolitan in his tastes long before the phrase "world music" had been coined, committed to radical causes long before the young activists of the universities joined the civil rights campaigns of Martin Luther King, turned on to the blues when it was still stuck in the ghetto, hitting the charts when most folk balladeers were trying to be John Jacob Niles or Peter Peers, he ploughed and planted a furrow that has nurtured more branches of pop than any other single musician, songwriter or singer.

Without Peter Seeger, there might never have been a Bob Dylan to be turned on to the untidy ballads of Woody Guthrie, published by the People's Songs organisation he ran for just three short years in the late 1940s, though their magazine Sing Out! survives to this day.

Without his espousal of the 12-string guitar as played by Huddie Ledbetter and its use to accompany songs like Turn, Turn, Turn, his setting of verses from Ecclesiastes, it's unlikely that Roger McGuinn and the Byrds would have had either the lyric or the Rickenbacker electric 12-string to fire their beginnings of folk rock.

Yet despite his "nice guy" image and the warmth with which he could surround audiences throughout the world, he was quite a hard man to get close to. He could be spiky and uncompromising on a personal level.

David King Dunaway tells the story, in his biography How Can I Keep From Singing, of how Pete once smashed up his own banjo in rage when people kept urging him to loosen up and drink at an after-concert party when he didn't want to.

I recall that when his manager Harold Leventhal and his British publisher David Platz borrowed my flat in London for a party in his honour, laying on a bunch of professional caterers to handle the food, Pete arrived, took one look at the spotless linen and silver candelabra, and walked straight out again. He wouldn't come back until the napery had been hidden away.

Yet this was the man whose folk group the Weavers used to don black tie and dinner jackets to sing to the Cafe Society crowd at places like Ciro's in Hollywood and plush joints in Reno, Nevada. Only a few months earlier, of course, they'd been rained with rotten tomatoes when singing for the American Labor Party from the back of a truck.

When I devoted an entire issue of my Folk Music magazine to "Seeger, negative and positive," he promptly offered me an article savagely attacking his lack of artistic merit - one it turned out he had written himself. I turned him down but it was later published in Sing Out!

He was less than fair to himself. At the height of his powers he had a rich, baritone voice - extending to a fantastic falsetto in songs like Solomon Linda's Wimoweh - and an instinct for the dynamics of a song which made him one of the best singing storytellers there's ever been.

Even in the closing years of his life, when his voice was shot, his rapport with his audiences could carry him through - that, along with his enthusiastic instrumental playing.

As well as the banjo and 12-string guitar he also popularised the halil, the Palestinian flute, and for a time used to accompany his performances of black work songs by chopping through a log with an axe. Thanks to this powerful piece of music theatre - and a dangerous one, too, if you were sitting in the front row and dodging the flying splinters - to this day guitarists call their instruments an axe, though I don't expect they know why.

He also played a significant part in popularising Caribbean steel pan music, shooting an early instructional film on how to make and play them.

He was a great encourager of others, both through his quickly written instructional manuals - which he was always lamenting he didn't have time to revise, even when they were selling in their thousands - and by postcards sent from wherever he happened to be, commenting on that new song you'd sent him or sending a cutting about something he knew you were interested in.

He was an incorrigible radical who didn't abandon his radicalism when he left the US Communist Party, nor when the McCarthyite blacklist made the million-selling Weavers non-persons in the fickle world of show business. Like Paul Robeson, his passport problems sparked off an international campaign for his freedom to travel, a battle he won without ever compromising his principles.

From 1968 onwards, he devoted much of his energy to ecology and in particular to the cleaning up of the Hudson river which ran near his home in Beacon, New York.

He fostered the building of a 106-foot sloop, the Clearwater, and crewed it with people like the New York cowboy Rambling Jack Elliot, a precursor of Dylan in adopting Woody Guthrie's hobo image, and Louis Killen, the Geordie shantyman from England.

At a time when student radicals were being shot down in Kent State and the FBI was systematically targeting the Black Panthers, Seeger's change of emphasis dismayed some of his radical friends.

But once again he was ahead of his time and the Clearwater campaign - "The price of liberty is eternal publicity," he quipped, looking up at the helicopters hovering over the launch of the sloop - led where many others have followed.

Yes, even today's eco-warriors are Pete Seeger's children too.

Karl Dallas