What better way for the founding fathers of British folk-rock to celebrate 45 years as a band than with an intimate gathering of 20,000 friends and family?

Fairport Convention's annual festival, held in the Oxfordshire village of Cropredy over three days last week, has been a fixture for fans of Britain's unique brand of electric folk music since their "final" outdoor concert there in 1979.

By tradition, the current five-strong line-up is supplemented at Cropredy by guest appearances from the band's numerous former members, who continue to exert a strong influence on the folk scene. But anniversary years are special.

"In a year with a 5 or a 0 on the end we tend to try to reflect on previous incarnations of the band without slavishly trying to become younger versions of ourselves," said Simon Nicol, a founding member of Fairport and festival co-organizer.

On stage for Saturday night's 3-1/2-hour closing set were some of the most feted musicians in folk-rock, including demon fiddler Dave Swarbrick and virtuoso guitarist Richard Thompson.

But playing alongside them was the new generation - including children of some of the Fairport legends, who are forging careers of their own - showing the folk music tradition of constant reinterpretation is alive and well.

Kami Thompson joined her father on stage, singing "Come all Ye," the opening track of Fairport's landmark 1969 "Liege and Lief" album, while Blair Dunlop, son of another of the band's founders, Ashley Hutchings, appeared alongside his dad. Singer Kristina Donohue and her father, guitarist Jerry Donohue, were both among the string of guests.

"One of the best things about the festival is when we bring our sons and daughters on," Hutchings told the crowd as he brought on Blair for a guest spot with Hutchings senior's band, Morris On, who play thumping electric versions of the songs that accompany the ancient reels of Morris dancing.

The set also included a display of the high-kicking steps of Morris, in which dancers wear bells on their legs and often wave handkerchiefs or clatter together wooden sticks.

"And it's nice to see you are bringing your offspring too," Hutchings added.

"Liege and Lief", with its mixture of ancient folk songs and Fairport originals played with the guitars and drums of a rock band literally electrified the British folk music scene.

It was controversial among traditionalists but helped unleash a wave of bands, from Steeleye Span and Lindisfarne arguably through to today's Bellowhead.

The "family tree" of musicians with a link to Fairport is as twisted as an old bramble and still bearing fruit.

Welsh band Calan, who sing much of their material in Welsh, appeared on Wednesday. Their latest CD was produced by former Fairport guitarist Maartin Allcock.

"I don't feel responsible for having enabled this," Nicol said. "But I think we did open the door ... a lot of music has come through that door."

The current Fairport line-up has been together longer than any other in the band's 45 years but Nicol says they have no problem integrating former members.

"It's that family thing ... you can't get out of your family, you can't divorce them. There is a continuity between us. You may lack the energy and optimism of youth but you develop coping strategies. You become more tolerant, patient and, hopefully, more understanding of each other," he said.

The relationship with the fans is close. The track list of Fairport's latest album "By Popular Request" was chosen in a poll of the 23,000 fans with whom the band is in email contact.

Many in the crowd were of similar ages to the surviving Fairport founders, who are all in their 60s at least, but they too appear to be passing the baton to a new generation.

Adam Webb, celebrating his 23rd birthday on Saturday, was taken to this festival exactly five years previously by his father, who introduced him to his own favorite folk bands.

"It's all because of my dad. If he didn't like them, I would never have heard them," he said. Webb, a soldier, said he would miss next year's festival, as he expects to be posted with the British army toAfghanistan.

As for the band, dates are already fixed for Cropredy 2013.

"This is a hugely vital part of my year. It is very energizing. There is such a feeling of support and community," Nicol said.