Director Christopher Nolan keeps throwing wild challenges at composer Hans Zimmer. First, it was reinventing the sound of a troubled hero for “Batman Begins,” then creating an unsettling vibe for the Joker in “The Dark Knight.”

For this year’s “Inception,” Zimmer faced a complicated story involving dream infiltration and a troubled protagonist’s tragedy-scarred marriage. Nolan wanted Zimmer’s music to “lead the audience in an emotional, visceral way through these different things,” the composer says.

Although Zimmer had read the script, Nolan refused to allow the composer to see any footage during editing. “He wanted my imagination to run riot,” Zimmer says, adding that Nolan asked him to “write the score independent of the movie.”

So Zimmer created a lengthy electronic “demo” containing all the key themes, musical development and orchestral ideas that would later take shape as a final score, complete with real musicians — including guitarist Johnny Marr of the Smiths and Modest Mouse fame.

“There’s nothing more appalling than rock guitar and orchestra,” says Zimmer with a laugh. Yet the composer felt like he was “channeling Johnny Marr” and ran the idea past Nolan and his producer-wife Emma Thomas, who turned out to be Smiths fans and said yes to the guitarist.

“The Fender Stratocaster is one of mankind’s greatest inventions,” Zimmer says. “Anybody can buy one, play it, and they will sound like who they are. There are not many notes to play — these notes were written, there was no improvisation — so it was really about the fingers on the strings of that guitar and the noise he makes.”

Getting the touring Marr to London for recording sessions between Icelandic volcano eruptions this past spring was trouble enough. But the soundscape for “Inception” that Zimmer had in mind was a complicated process that involved live musicians, electronic manipulation and then re-recording the manipulated sounds in another acoustic environment — “dreams within dreams,” like the plot of the film.

Zimmer was in London last December for the premiere of “Sherlock Holmes” when a conversation with Nolan prompted a hastily organized session for 22 brass players at George Martin’s AIR Studios. Twelve trombones, six French horns, four tubas “and nothing written,” quipped Zimmer.

“We explained to them the noises we wanted them to make,” the composer says. “Any note at random, within a certain range. Dissonance, played beautifully, is incredibly evocative.” Sympathetic resonance from the strings of an open piano also proved useful.

Zimmer says “we really did try to create a sonic world” specific to “Inception.” In addition to Zimmer’s purely electronic starting point, Marr’s guitar work and the brass clusters, there were multiple London sessions for 32 strings and 20 more brass players. “Not only did we get the orchestra in certain places to imitate electronic sounds, at other points we would take electronic sounds and re-mic them,” he says, including experiments with speakers in stairwells at AIR.

Zimmer estimates that the score was about 60% electronic, but so much of the music was manipulated that actual numbers may be a matter of interpretation.

The classic Edith Piaf song “Non, je ne regrette rien” plays a critical role in the story, and it was up to Zimmer to interpolate it into the film’s complex sound design. They went to the French National Archives to obtain the 1960 master and then used sophisticated audio techniques to isolate her vocal for use throughout the film.

Not all of Zimmer’s grandiose ideas worked: “You should have heard my dissertation about how to slow down the spectrum within a sound as opposed to slowing the whole sound down,” he says. “The science didn’t quite exist. We would have had to go to Geneva to use that Hadron Collider (the high-energy particle accelerator, which some theorize could facilitate time travel). Warners just wouldn’t spring for that.”

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