It is a rock classic; a groundbreaking album which rewrote the rules of musical production. Mike Oldfield’s 1973 classic Tubular Bells is a towering achievement featuring more than 30 musicians on a bewildering number of instruments. So imagine the album being played live, with no trickery... by just two lads from the wilds of Australia.

Aidan Roberts and Daniel Holdsworth sound like your typical carefree Aussies. But they are musical wizards, pulling off what anyone with an ounce of sense would have dismissed as a joke — playing this complex musical masterpiece, with 26 instruments, in front of an audience — with just their hands and feet.

“It is no mean feat!” laughs multi-instrumentalist Aidan, 34, who is getting stuck into a five-week European tour to celebrate the 40th anniversary of the album’s release.

“It requires an enormous amount of concentration,” he says. “It is exhausting — especially while leaping around stage like a madman.

“But the adrenaline rush is enjoyable. If we had a week off we’d go insane.”

So how did two friends from the Blue Mountains end up on the other side of the world, performing a faithful, note-perfect rendition of one of the greatest albums of the ’70s?

“It was really Danny’s idea,” says Aidan, a founding member of psychedelic folk-rock group Belles Will Ring, who writes theatre scores and plays under the name The Maple Trail.

“I’m a good songwriter but a terrible guitarist so I was getting some tuition from him. One day I happened to have Tubular Bells on at home and Danny notated the first seven minutes for two guitars.

“It was fun and we thought that was that. But after learning the first part we thought ‘why not carry on?’ We got carried away.”

The sheer size of the project soon became obvious — but they weren’t giving up easily. “To notate the whole thing would have taken months, so we drew maps and flow charts of how it works, and learned by ear. And we decided to perform it — and again got carried away.”

Beginning with just guitars, the instruments multiplied, eventually filling Aidan’s home. “We had pianos, a kick drum, mandolin and glockenspiel, and decided to expand until it became the lunatic circus you see today which sounds pretty much like Tubular Bells.” They played it live at a club in Katoomba, New South Wales, expecting only to see a few family members and friends. The show sold out and was so well received they were invited to play the Sydney and Edinburgh Festivals — winning awards at each. And, Aidan says, they are improving all the time.

“We have to be inventive but also keep the spirit of the original,” he says. “It’s quite densely populated and has taken hundreds of hours of rehearsing to get it right... and seamless.” Does he ever tire of it? “No, though I need a break from it every now and then. Going home with those melodies in your head can get a bit maddening. But we are not a covers band and we do pursue other interests. Every performance is different, too, that keeps it fresh.”

The inventory of instruments now includes electric, bass and acoustic guitars, synthesizer, piano, glockenspiel, drum kit, kazoo, tin whistles, bodhran, electric organ, loop, distortion and delay pedals, their own voices — and, of course, tubular bells. Aidan describes the show as “one album, two men... too many instruments,” which, he admits, involves a lot of co-ordinated jumping around. “It’s like a ballet,” he says. “Some sections have a lot of detail, which is hard with the amount of limbs we have. But it all comes down to what our fingers are doing. It’s relentless and once you start you’ve got to keep it on the rails. But we are getting better and better. And the audience love it.” He adds: “We’ve taken a lot of care with where we place things on stage to make things easier to reach — and also to add to the dramatic impact. It does have a shape and it looks pretty cool.” On its release, Tubular Bells, which was recorded at Shipton-on-Cherwell, was a massive hit, selling 25 million copies and launching the Richard Branson Virgin empire. “It was a huge hit record and truly went round the world,” he says. “We love it. It’s great and is so indicative of the time and is still a great record to listen to. It was the crowning achievement of the time and of Mike Oldfield’s career.

“It’s simple, honest and not pretentious. It’s like an orchestral, folk, cinematic journey with a film score quality. And it was recorded on the cusp of when analogue recording technology was reaching its peak.

“You can do anything you want with a computer as long as you’ve got the hard disc space, but there’s something about technical limitations that make the work stronger. What you leave out is as important as what you put in.”

And there is a whole generation who may not have heard it, so they are also introducing it to a new audience. “It’s very beautiful and sometimes I get quite moved by it. Other times I just want to go to bed!”

  • Tubular Bells for Two
  • New Theatre, Oxford Tomorrow (Friday)
  • Tickets £23.90 from atgtickets.com