(CNN)For "La La Land," the movie is the music.
While the musical didn't win the Academy Award for best picture (at least not in the end), "La La Land" composer Justin Hurwitz did take home two Oscars .
"La La Land" makes its Digital HD debut Tuesday. In a recent interview with CNN, Hurwitz described composing the film's Oscar-winning signature tune "City of Stars."
"Everything starts with me sitting at the piano for a very, very long time, going through one melody idea after another, after another. Throwing them out. Sending them to [director Damien Chazelle]. Then, throwing them out. Until we have the right melody or melodies," Hurwitz said.
In "La La Land," Ryan Gosling begins to sing "City Stars" by whistling. According to Hurwitz, that opening had a few false starts.
"I was visiting my parents in Wisconsin. I was coming back to L.A. that day. I was just packing my stuff up at their house. We were heading off to the airport. Damien and I were still emailing back and forth about, 'Oh, this whistle. Should we have a whistle?'... I was so in the middle of it. I didn't want to have to put it down to go to the airport and fly," Hurwitz said.
Hurwitz described telling his parents to stop the car so he could record himself whistling on his computer before sending the demo to Chazelle.
"He'd email back, being like, 'Oh, yeah, that's interesting. Can you try this instead?' I'd be like, 'Hey, can you guys stop the car?' Then, I would whistle again," Hurwitz said.
Hurwitz and Chazelle are a symbiotic creative team. Hurwitz also composed the music for Chazelle's "Whiplash" and "Guy and Madeline on a Park Bench."
Their next project, the Neil Armstrong biopic "First Man," is a departure from the musical genre, but they're still working closely together on the film.
"We're already talking about the soundscape and score ideas," Chazelle told CNN earlier this year. "That [music] will always be at the center of everything I do."
Hurwitz wouldn't reveal any details about "First Man" when asked, but Chazelle promised some familiar themes.
"To me it became, or it's becoming a story about sacrifice, and in some ways like 'La La Land' or 'Whiplash,' having the dream and the cost of pursuing that dream, the price of it, the cost of pursuing any goal on a very personal level," Chazelle revealed.
As for the pursuit of success explored in "La La Land," Hurwitz shed light on the musical's ending -- a reflective look at the love between Emma Stone's Mia and Gosling's Sebastian, set to Hurwitz's score.
"What if everything had worked out? What if all of the dreams had come true and everything had worked out?" Hurwitz said. "How are we going to take all of these motifs and all these melodies from the movie and use them to revisit points of the story and use them to revisit this larger idea of what could have been?"