LONDON (Reuters) - One of the more startling moments at the London concert by British folk band Moulettes this weekend was when founding member Ruth Skipper turned her bassoon into an instrument of industrial rock.

As bass and drums hammered out a heavy beat and an electric fiddle and wired cello soared to feverish heights, Skipper turned from the audience, bent near double and roared out a riff that would have done a Moog synthesizer proud.

"It's not the most practical instrument to play. But it works," said Skipper, who also sings and plays autoharp. She added that that her venerable classical woodwind was played through an electronic filter.

Welcome to the world of prog folk, an unusual marriage of traditional British folk music with the prog - or progressive - rock that dominated alternative music in the late 1960s and early 1970s.

Moulettes are among the current leading UK practitioners of the sub-genre. They are like a cross between Pentangle and the Kronos Quartet, by way of Kate Bush and early Pink Floyd's Syd Barrett.

The band members are not oldies seeking to reinvent their youth. In their 20s and 30s, they are a new generation to embrace the music, coming from diverse musical backgrounds and clearly relishing the opportunity to experiment.

Not so much, however, that it did not afford Saturday's delighted audience a chance to test the Islington venue's sprung floor with some appropriate foot-stomping.

"You just absorb music as a sponge if you're involved in it," said Hannah Miller, who fronts the band as lead singer and cellist.

Miller said she did not think of the band as folkies - despite the jig-like elements of some songs - but liked the story-telling that goes with that genre.

Indeed, she is writing a book based on the stories in Moulette songs, which range from light-hearted romps such as Sing Unto Me to seemingly darker offerings like Bloodshed in the Woodshed.

Miller, meanwhile, said the five-member band - joined on and off by a cadre of guests with harp, kettle drum, saxophone, tubas and the like at the Saturday event - all like prog music.

They have credentials to prove it, too. Double-bassist Jim Mortimore is the son of Malcolm Mortimore, the drummer with 1970s British progressive rockers Gentle Giant.

And the band's current guests include self-styled "God of Hellfire" Arthur Brown, whose band The Crazy World of Arthur Brown had a huge global hit with Fire in 1968.

Brown appeared on stage for one song with Moulettes on Saturday. He was draped in black, head covered by a quasi-Mongolian hat, and face painted in stripes. You can't get much prog-ier than that.