Jethro Tull, York Barbican Centre, February 18

IAN Anderson's radio can be heard in the background, tuned to Classic FM.

This is not a sign of the changing tastes of the passing years - the Scotsman is 56 - but a reminder of how he introduced the classical flute into rock music in the music of Jethro Tull.

You may call them a folk rock institution; the Guinness Rockopedia less politely pins them down as "folk prog oddities". Whatever, Ian Anderson and fellow founder Martin Barre and their colleagues Andrew Giddings and Doane Perry are still ploughing a distinctive furrow 36 years since Jethro Tull took their name from the 18th century inventor of the seed drill.

On Wednesday, on night six of 14 February dates, Jethro Tull will be appearing at a sold-out York Barbican Centre, where Barre will open the show in the company of friends such as Willy Porter in a showcase for his latest solo album, Stage Left. Tull will follow, performing songs new and old, spanning 1968 to 2004 and all points between.

"We try not to repeat ourselves," says Anderson, on the phone from his West Country home. "We check the set list from everywhere we play to make sure the set will be 80 per cent different from the last time."

He is notoriously meticulous, even scholarly, as his authoritative, on-going programme of Jethro Tull re-releases confirms, but he is grateful too for the contributions of Tull aficionados.

"In this age of fan websites, we can avail ourselves of those set lists from the web to work out the optimum set list to illustrate the different styles and different eras of the band. This way we can highlight our landmarks without playing the same songs again and again."

Bringing the live show up to speed in York, Tull will play a couple of songs from Anderson's fourth solo album, 2003's Rupi's Dance, alongside a selection from last October's Christmas Album, including Tull's interpretation of God Rest Ye Merry Gentlemen and a piece from Faure's Pavane.

"We're also going back to our first album This Was in 1968, and it's weird that something from that time does not seem of that time but can feel contemporary. The live arrangements bring the songs forward to at least the Middle Ages!"

The Christmas Album likewise straddles ancient and modern, through its combination of exuberant Christmas carols, new material and re-recorded Tull pieces on a Christmas theme.

How did the record come about? "Two days before Christmas 2002, I got a call from our American office saying 'How about Tull doing a Christmas album?'. My immediate reaction was, 'Oh god, how do we wriggle out of this, but I promised to respond within 24 hours," says Anderson.

"In that time, my thoughts turned round completely, and I realised we'd done Christmas pieces over the year and I thought there would be a challenge in writing some new Christmas songs

"I knew that would be difficult because everything that needs to be written for Christmas has already been written, from Bing Crosby to Slade, and without being Bing Crosby on a flute, we had to do something different."

His solution was to reflect Christmas beyond the traditional holly and jollity. "Without wanting to make a record that was too grumpy, I wanted to do an album that came from the other side of Christmas, the alternative moods of Christmas."

This week, Jethro Tull's latest digital re-masters are being released by EMI Records, namely the 1978 live album Bursting Out, 1979's Stormwatch (with bonus tracks) and 1980's A (with a bonus DVD of Tull's Slipstream video).

"There's always a re-mastering of our catalogue going on, though it should come to an end in about two years' time," says Anderson, who oversees the re-release programme and writes new liner notes for each album.

"When completed, there should be about 25 re-masters. Even some of our compilations are being re-mastered because in their own right they have become works not to be deleted."

Will Tull be recording new material this year? "There are not any plans for not recording. But looking at the plans for the year ahead, there are lots of short excursions and three-week tours, and I've just come back from India, where Tull played with the revered classical Indian flautist Hari Prasad Chaurasia, the Ravi Shankar of the flute" says Anderson.

"I've also got eight or nine shows with orchestras coming up in Italy, travelling from the north down to Sicily. That's something where I do some of my solo music, and some Jethro Tull music, in the context of orchestral settings.

"My idea with these shows is to radically re-arrange rock songs to make them really quite different, so that the songs are strong musical forces in their own right. I don't just tag an orchestra on to a electric guitar, because I find that a violin and electric guitar don't sit well together. An acoustic guitar fits better with orchestral settings."

Whether playing in Dubai for the first time this winter, or performing with Chaurasia, Anderson is always seeking fresh musical experiences.

"One of the difficulties with the Indian concerts was that they sit cross legged, so I'd sit like that and then have to race across the stage to stretch my legs and stop the cramp, without insulting them by being too rock'n'roll" says Anderson.

Cross-legged? It certainly made a change from all those years of Anderson playing his flute perched on one leg.

Jethro Tull, York Barbican Centre, February 18, 7.30pm. SOLD OUT. For returned tickets only, ring 01904 656688.

Updated: 09:12 Friday, February 13, 2004