Call it a case of putting the musical cart before the filmic horse.

While the overwhelming majority of movies -- especially big budget Hollywood tent-pole films -- hire soundtrack composers only after all the footage has been shot, “Tron: Legacy” director Joseph Kosinski approached the French dance music duo Daft Punk about composing the film’s score a full two years before cameras rolled. His thinking was, the group’s mash-up of electro-rave beats and symphonic orchestral compositions would set an emotional tone for the sci-fi thriller’s futuristic scope and sweep.

Band mates Guy-Manuel de Homem-Christo and Thomas Bangalter experimented with different musical textures, but ultimately decided -- in what initially came as a surprise to both Kosinski and “Tron: Legacy” distributor Disney Studios -- that the kind of big-beat electronica for which they are known was all wrong for the movie. Instead, the group went in a more orchestral direction that almost nothing in its musical oeuvre suggested they could pull off.

“There was this idea to find influences that could be 400 years old -- or 400 years in the future,” Bangalter said. “To properly establish a timeless quality that suggests both the future and the past.”

After a year and eight months of work on the project, Daft Punk and music arranger and orchestrator Joseph Trapanese decamped to London’s AIR Lyndhurst studios to record with an 85-piece orchestra over the course of a rapid-fire session that lasted less than a week.

“It was both exhilarating and very emotional,” recalled Bangalter, a slender, thoughtful guy with a shock of unruly hair who does most of the talking for the group in strongly accented but flawless English. “And at the same time it was completely terrifying. You were working a year and a half on pieces of music that you had five days to record.