NEW YORK (AP) -- When Robert Lepage signed on to direct the Metropolitan Opera's first new "Ring" cycle in more than 20 years, he saw his challenge as using high-tech wizardry to create a set that would mirror Wagner's unique musical style.

That meant finding a visual equivalent for the "leitmotivs" or thematic strands of melody that Wagner wove in ever-shifting forms to compose the score of his epic music drama.

"All the motivs are like coloring crayons," Lepage said in a recent interview during technical rehearsals. "You take one theme and another and another and you do a braid with them and you create yet another. You always have the impression that the music is new and that the situation is new, but it's sewn or threaded with always the same threads. So we were looking for a set that would be devised in the same way."

The set he came up with — unlike any ever seen on an opera stage — will be put on public view for the first time Monday night when the company opens its season with "Das Rheingold" ("The Rhine Gold"), first of the four operas that make up the cycle. The exceptional cast stars Welsh bass-baritone Bryn Terfel as Wotan, king of the gods, and American mezzo-soprano Stephanie Blythe as his wife, Fricka.

It's a 45-ton metal structure consisting of 26-foot towers at either end of the stage with a horizontal bar running between them that supports 24 planks. The planks move independently, rotating in any direction or bending in the middle so that they can take on an almost infinite number of shapes and angles. With the help of computerized projections, they morph into the waters of the Rhine one moment, trees in a forest the next, a staircase, an underground cavern, or the hands of a giant.

The same set will be used for each of the four operas, which will be introduced over two seasons, with complete "Ring" cycle performances in the spring of 2012 and 2013.

"We've given it many nicknames," said the Canadian director, who supervised construction of the set at a shop in Montreal owned by his production company, Ex Machina. "At the beginning, each of the planks looked like a giant seesaw, but then it became more sophisticated. So now we mostly just call it The Machine. Sometimes, as a joke, I refer to it as The Monster."

Some of the singers are being asked to undertake acrobatic exertions familiar to anyone who has seen Lepage's Cirque du Soleil extravaganza "Ka" in Las Vegas. The Rhinemaidens sing their opening measures while "swimming," suspended by wires; tenor Richard Croft, playing the role of Loge, the half-god of fire, has to scamper backward up a steeply slanted ramp, helped by wires connected to his body.

Other effects will be created by using body doubles wearing the same costumes as the principals.

"You don't want to have Bryn Terfel with his head upside down hanging from a branch," Lepage said. "I want him to be in shape and sing."

And, indeed, the main characters — dressed in costumes that are highly traditional — spend most of their time interacting with each other very close to the front of the stage, or apron, while the set does its thing as a backdrop.

A lot is riding on the razzle-dazzle potential of The Monster, beyond the roughly $16 million price tag for the new production — which doesn't count several hundred thousand dollars it cost to reinforce the stage so that it could support such a heavy structure.

The Lepage "Ring" is replacing a much-loved, deliberately old-fashioned production by Otto Schenk that was introduced starting in 1986 and given its final outing in 2009.

And adding to the buzz that always surrounds a Met opening night, "Rheingold" will also mark the return to the conductor's podium of music director James Levine for the first time since health problems took him out of action last February.

But for all the focus on the set, Lepage knows this "Ring" will be judged as much by how well it depicts the conflicts among the characters as by the special effects.

"The thing I've learned through this process with James Levine is that even though it's a gigantic opera, it's a very intimate story and you need the main characters to be with you on the apron."

Peter Gelb, the Met's general manager who hired Lepage in 2005 and who has been a watchful presence throughout the long rehearsal process, agrees that "for any production of Wagner to succeed, it's all in that intimate storytelling."

Gelb is hopeful that Lepage has found the right balance.

"I love the contrast between the visual 'coups de theatre' and the intimate, almost kabuki-like interplay of the characters on the apron," he said. "They are so far downstage and in your face. The big visual moments work to accent the straight drama."

Yet Gelb admits to some pre-opening night jitters, something he said he always feels — but perhaps more so this year.

"This is obviously a project that has taken more time, care and attention than anything else since I've been here," he said, seated in the half-lit auditorium during the rehearsal break. "To the extent that I can will it to be right, I'm here doing just that."