Before she became famous as a master of intricately stacked cyborg harmonies, the British singer-songwriter Imogen Heap was one half of Frou Frou, an electro-pop duo who didn’t last long but who had a couple of moments in the cultural spotlight. Heap started working with producer Guy Sigsworth when she was 17. They only released one album, 2002’s Details, before breaking up in 2004. At the time, they were probably best-known for the version of Bonnie Tyler’s “Holding On For A Hero” that appeared in Shrek 2. These days, they’re more famous for a different cinematic moment.

In 2004, right around the time that Frou Frou were breaking up, Zach Braff used their Details opener “Let Go” in his directorial debut Garden State. That movie’s soundtrack played a big role in indie rock’s growing mainstream visibility. Frou Frou were never an indie rock band, but “Let Go” became part of that conversation. Yesterday, the Ringer ran an oral history of the Garden State soundtrack, and Imogen Heap makes the startling revelation that “Let Go” was actually written for a very different movie.

It turns out that Frou Frou wrote “Let Go” for Phone Booth, the 2002 Joel Schumacher thriller where Colin Farrell spends the full running time trapped in a phone booth, dealing with tense threats from a never-seen Kiefer Sutherland. Phone Booth was a hit, but it didn’t have any music-world resonance, so I guess things worked out well for Frou Frou even if they didn’t make the cut for Phone Booth. Here’s what Heap says about it:

“Let Go” was originally written for a film called Phone Booth. It had a much bigger energy, much bigger drums, very intense. I always loved the song, but it didn’t get into the movie. Then one night in our studio in West London, I brought out my cello. We stripped away all the intensity, and we were just left with the strings and the voice and that amazing bass line. We loved it so much, but through that whole Frou Frou album [Details], nobody really got to know about it until after Garden State.

In the article, Heap also thanks Thom Yorke. “Let Go” plays at the end of Garden State, and Zach Braff was originally hoping to use Radiohead’s “Sulk” at that part of the film. Braff says, “Of course it would have been a huge Hail Mary try, but as I recall, what happened was we found a song that just works better. We didn’t need to make the insane ask of Radiohead.”

Read the oral history of the Garden State soundtrack here.