Kristen Anderson-Lopez and Robert Lopez wrote “Let It Go” for Frozen within a single day. Conception began when the story outline they were given called for “Elsa’s Bad*ss Song” at the scene the song would take place, but the two began by envisioning the song with an “emo” undertone. According to Anderson-Lopez: “We went for a walk in Prospect Park and threw phrases at each other. What does it feel like to be the perfect exalted person, but only because you’ve held back this secret? [Lopez] came up with ‘kingdom of isolation,’ and it worked.”
Lopez was able to improvise the song’s first four lines on the spot. They went home and composed the rest of the song by alternating between improvising melodies on a piano and brainstorming lyrics on a whiteboard. Musically, the song was written to accommodate Idina Menzel’s vocal range. “Let It Go” went on to break a number of pop music records; becoming the first song from a Disney animated musical to reach the top ten of the Billboard Hot 100 since “Colors of the Wind” from Pocahontas (1995) peaked at number four.
“Let It Go” is also Menzel’s first single to reach the top 10 on the Billboard Hot 100 chart, making her the first Tony Award winner for acting to ever reach the top 10. “Let It Go” won the Academy Award for Best Original Song at the 86th Academy Awards, where it was performed live by Menzel. – IMDB