Diane Warren on Her Lady Gaga Collaboration for New Documentary 'The Hunting Ground'

Emily Shur

Diane Warren photographed at her piano.

The most talked about song at the Sundance Film festival is one that very few people have heard: Lady Gaga's "Til It Happens To You" from The Hunting Ground.

Sundance 2015: Full Coverage

Diane Warren, Oscar-nominated this year for "Grateful" from Beyond the Lights, wrote "Til It Happens To You" after being shown scenes almost a year ago. She took the song to Gaga -- sharing a writing credit with Warren -- who quickly recorded it.

"I heard about [the film] and it just really touched me," Warren tells Billboard in her first interview since The Hunting Ground premiered Jan. 23, "and she had stuff in her life that she could relate to. Gaga is one of the most talented artists I have worked with in my life and I'm excited about doing more with her."

The song appears in the body of the film to underscore the pain of a survivor of sexual assault. Another version closes the film, which will be released March 20 and air later this year on CNN.

"There are a lot of levels to the song," says Warren , who saw the finished film for the first time at the premiere. "There's something very vulnerable about it and something very defiant about it, especially the way [Gaga] sings it. The first verse is vulnerable -- 'You tell me its going to get better?' -- and the second verse comes in and it builds. Really? It gets better? No. You don't know until it happens to you."

Like "Grateful," which Warren describes as a song that celebrates success at the end of a trying time, Warren hopes the song has a life beyond the film.

"I think this song in particular can relate to anything you want, anything in your life," she says. "It could be a breakup, somebody passing away -- anything where there is loss and someone says to you it's going to be all right, it just takes time, but you're sitting there dying. It's such a universal song."