ON A Tuesday afternoon last December, the Orchestre Métropolitain, a 48-person choir and the singers of L’Opéra de Montréal gathered in a rehearsal room for their first run-through of an ambitious new opera. Part-way through one number came an ominous rumble of timpani and a creeping darkness from the double basses as a baritone full-throatedly announced: “I have become…comfortably numb…”

One of the more remarkable new operas of recent times will open in Montreal on March 11th: “Another Brick in the Wall”, based on Pink Floyd’s double-album “The Wall”. According to Opéra de Montréal, tickets have sold in record numbers; it has particularly drawn people who have never been to an Opéra de Montréal production before.

But any Floyd fans hoping for a rock-classical treatment of the material—a violin version of David Gilmour’s journeying guitar solos, for example—are in for a bad trip. There are elements of the original embedded in the score, such as the forceful opening chords of “In the Flesh?” and the rising-falling riff of “Another Brick in the Wall”. Apart from that, those intimately familiar with the source material may be the most disorientated of all: in some moments, the original vocal melodies are performed by a soloist or choir in resonant operatic tones—while the orchestration underneath is utterly unrecognisable. Julien Bilodeau, the composer, stresses that the opera is tonal, tuneful and relatively accessible, steering away from intimidating atonalities. But “Another Brick in the Wall” is not designed to mollycoddle any prog-rock enthusiasts. “If you know the album well, you’re going to hear a lot of things that you already know,” Mr Bilodeau says. “But if you want to hear the album you’re better off listening to it in your living room.”

The 42-year-old composer has genuine Floyd-fan bona fides himself, with fond memories of practising Mr Gilmour’s guitar licks as a teenager. Even so, he says, the process of delving into and drawing on the music of “The Wall” was one of discovery. “I went very, very far into it. I think it’s going to be a very long period of time before I listen to ‘The Wall’ again.”

The project has the approval of Roger Waters, Pink Floyd’s former bassist, singer and the driving creative force behind the band’s most celebrated years. But Mr Waters admits to having initial doubts. “In my experience, the marriage between rock’n’roll and any kind of symphonic form always ends in disaster,” he says, chuckling wryly. He includes his own foray in this: In 2005, Mr Waters released his own opera, “Ça Ira”, to middling reviews. “By and large it’s a really bad idea.” One of the best-selling albums of all time, “The Wall” spawned a film and three live albums (one from the full band, and two from Mr Waters since his acrimonious split with the band). An opera is quite another proposition, though. With low expectations, Mr Waters agreed to meet with Pierre Dufour, former executive director of L'Opéra de Montréal and the mastermind of the project, Dominic Champagne, the director, and Mr Bilodeau. At the meeting, Mr Bilodeau presented demos of two drastically reimagined versions of pivotal tracks from the record: the scorching curtain-raiser “In the Flesh?” and the sneering sing-along “Another Brick in the Wall, Pt. 2”. Mr Waters was impressed. “By the end of the afternoon I had to change my position. ‘All right. Let’s go for it.’” “Another Brick in the Wall” uses his original lyrics and the essential plot of “The Wall”, which traces the downfall of a rock star named Pink into madness, paranoia and eventual mutation into a fascist dictator-figure. Mr Waters, who was five months old when his father was killed in the second world war, has called the record semi-autobiographical. Mr Bilodeau notes that it is also a story of appropriately operatic dimensions. “We all have that kind of tragedy in our lives. We all have scars we carry all through our lives. It’s really a human story,” he says. Added to the drama is the fact that “the Greek heroes of our era are rock stars. They’re gods. And we’re cheering them on like animals.” Mr Bilodeau was five when “The Wall” was released in 1979, but the fearlessness with which Pink Floyd explored diverse musical terrain has informed and inspired Mr Bilodeau’s own approach. “Another Brick in the Wall” will feature a keyboard synthesiser and myriad ambient sound-effects, nodding to a couple of the band’s sonic trademarks. “We’re going to make the same kind of sound exploration that we’re used to with Pink Floyd,” Mr Bilodeau says, but he knows where to draw the line. “I wasn’t going to put drums on it,” he notes, cringing at the thought. “I believe in it as an opera piece.”

“Another Brick in the Wall” is showing at L’Opéra de Montréal until March 27th