Arcade Fire's Will Butler on Co-Writing Best Score Oscar Nominee 'Her,' The 'Intimidating' Sex Scene (Q&A)

William Butler of Arcade Fire performs onstage at Capitol Records Studio on October 29, 2013 in Hollywood, CA

Mike Windle/WireImage

Arcade Fire took a break from recording its fourth studio album, "Reflektor," so a few of its members could score the Spike Jonze stunner "Her." The film is nominated for Best Picture at this year's ceremony and Arcade Fire's Will Butler and indie-folk artist Owen Pallett are up for Best Original Score for their music from the film. The categories other nominees are: John Williams for "The Book Thief," Steven Price for "Gravity," Alexandre Desplat for "Philomena" and Thomas Newman for "Saving Mr. Banks."

Billboard: You spent 14 months working with multi-instrumentalist Owen  Pallett as "Her" was developed. Spike Jonze said it felt like he was jumping into the band. How did it feel for you?
Will Butler:
It was awesome to be there for the whole arc of it -- like collaborators, not guns for hire. I joke about putting out a 10-CD "Her" soundtrack boxed set.

Did the soundtrack change when Joaquin Phoenix's co-star Samantha Morton was replaced by Scarlett Johansson during postproduction?
Yes, radically. The movie got less high-concept and became more about these two people. The music did the same thing: It started in a "Blade Runner" world and slowly became more piano-centric and less epic, with strings and warm synthesizers.

What was the toughest scene to write for?
The last six minutes. We did five or 10 takes over two days. Working with a band, there's a push and pull that's very different from a single thought going forward. We're just rock musicians; we don't know how to do it. It just happens.

How was composing the off-camera sex scene?
Intimidating. In the rough cut, the screen goes black, and it's sex noises for three minutes. You're like, "Oh, this could go wrong in so many ways -- like an infinite number." But we realized some of the emotional stuff from the album fit this world as well, particularly such a heavy romantic scene. I mean, it's the most "Gone With the Wind-like cinematic music in "Her." I didn't think we were going to get that sex scene done. It was the last day we could work on the film. We were telling Spike: "We have to put out our album and switch gears. ...You'll have to hire somebody who can actually compose for film." The last day, it was just me on piano and [Arcade Fire bassist] Tim Kingsbury on dreamy electric guitar. I think it was just one take, and we got the emotional core of it. We had chills, and we knew: "This works. There's magic here."