Better known for scoring such theatrical films as The Social Network and The Girl With the Dragon Tattoo, composers Trent Reznor and Atticus Ross turned their focus to climate change for Before the Flood, a new documentary from Leonardo DiCaprio and Fisher Stevens that debuts on the National Geographic Channel on Sunday.

The Nine Inch Nails collaborators went far beyond composing music for the film -- they brought in fellow Oscar-winning composer Gustavo Santaolalla (Brokeback Mountain and Babel) and Scottish band Mogwai to work on the score with them. Plus, they wrote the end-title song, the poignant “A Minute to Breathe,” which features Reznor’s first new vocal performance in a few years.

“Since seeing The Social Network, I’ve been moved by scores from Ross and Reznor," Stevens, who directed the film, tells Billboard. "There is something about their music that is emotional and has a bit of drive to it, and its aesthetic is like no other I’ve heard. Having them agree to participate in this film was a dream. I had used a lot of their tracks in temporary scores, even before I made the call asking them to be onboard. Little did I know their work ethic matched their brilliant talent.”

Stevens adds: “In documentaries, I think it's particularly challenging to unify the music with the film and transition between scenes, which is another reason why I wanted their expertise in scoring the film. Their music helps complete films.”

Reznor and Ross talked to Billboard about why they were so compelled to work on the film, and they also offered an update on Nine Inch Nails. Their next project is the Peter Berg-directed Patriots Day, starring Mark Wahlberg, about the Boston Marathon bombing.

How did you get involved in Before the Flood?

Ross: A couple of years ago I briefly met Fisher on a turtle sanctuary in Ojai [California]. He’s friends with my cousin, who sent me an email and said Fisher was working on something. I’m a fan of his documentary work. He [showed me] some of the scenes. I thought it was really great. I knew I was coming to see Trent and be here for the year. I had conceptually brought up the idea to Fisher how [Trent and I] might take on some and then start thinking about people we might like to collaborate with to fill it out. That’s basically how the whole thing started.

Trent, what were your thoughts?

Reznor: When I saw it, it was something we felt we needed to be involved with -- the fact that the country’s even debating about the science of this seems absurd and we related to it and wanted to help in some small way. We also thought it would be an opportunity to work with some people that we respected and could collaborate with so we reached out to Gustavo and Mogwai. We showed them the film and we didn’t talk about what scenes we’d be scoring; we just started to collaboratively write some music we felt like might be in the same wheelhouse for this film.

How did that process work?

Reznor: We made the decision to share our work in progress between the three camps. Something really interesting happened where we’d send out something that wasn’t finished and the next day Gustavo sends it back with a whole new section playing over parts of it and that led us to then modify what we were doing and incorporate that. And vice versa -- he sent us works in progress, demos, we’d start to have a trailhead of his piece and then steer it off the tracks into something with a different turn and send it back and say, "What’d you think of that?" The same thing happened with Mogwai. The nice thing about it was -- and this was a real motivation for doing this in the first place, aside from the selfish desire to collaborate with these people -- is it gave the film a holistic feel where the pieces felt connected. And, although coming from different camps and a variety of styles, it felt interconnected like a cohesive work. We didn’t want it to feel like needle drops. We learned something in the process and we made some good friends and I’m certain we’ll so something in the future together.

Were you and Gustavo and Mogwai ever face to face?

Reznor: All of this took place via online and telephone. Atticus had known Gustavo through a pre-school interaction and I met him at a showing at Fox and again, I can’t overstate this, we developed a real friendship in the making of this, and that has real value to me.

Ross: He has a daughter named Luna and I have a son named Wolf and they are genuine friends, so there is a connection there and I utilized it to our advantage.

How closely did you work with the director, Fisher Stevens, who also worked on docs The Cove and Racing Extinction?

Reznor: We got the feeling from Fisher there was a lot of work to be done in not a lot of time with the urgency of getting this out to the world pre-election, which we also are excited about the idea of that. So we kind of felt the need to step up and say, "Don’t worry about the music, we’ll do the heavy lifting."

Ross: But we were probably on the phone to Fisher every day or every other day. It was a close collaboration.

Reznor: It was a very tight schedule with minimal notice to everyone involved, but I think it benefited from that. It forced decisions to be made, and the end result is everyone felt really good about it.

What was the most challenging part?

Reznor: Quite frankly, the composing aspect, the collaboration aspect, all went pretty effortlessly. The most difficult aspect was the song “A Minute to Breathe.” That was just because we were very concerned -- this is the first time we have written a song specific with lyrics, recently, on a subject matter that matters to us, and we’re not trying to hit you on the head with literal interpretation. There was a choice to make it very naked and honest and I was singing in a register I don’t think I’ve ever sung in before, and it felt very uncomfortable by design. I think Atticus was getting tired of my own insecurity and was like, “It’s good. Get out of the room and let me finish it and don’t come in here second-guessing everything.” We probably spent three weeks just on that track, but it felt, again, it was self-imposed. That is part of our process, and now I feel good about it.

Was writing the end-title song part of the deal from the beginning?

Reznor: We didn’t even think about it until we started on the path starting the composing process, and then I had the idea maybe it would be an interesting challenge to see if a vocal song could work its way in somewhere. So without telling Fisher or anybody, we just worked on it and sent it over and said, "We think this could live in the film somewhere if you agree," and there was a very positive response from him. It wasn’t what we signed up for, it was one of the added bonuses of hiring us to score.

Where are you with new Nine Inch Nails material?

Reznor: It’s been something we’ve been kicking around and it’s gone through a lot of evolutions. I think it’s winding up at a place where we feel really good about it, and when it’s ready to be unleashed, it shall be unleashed.