After creating the music video for "Chandelier" in 2014, Sia decided she was "pretty good" at directing and "felt a little bit braver". The film's screenplay was co-written by Sia and children's book author Dallas Clayton based on a one-page story that she had written in 2007. Sia enjoyed the creative process and noted similarities between directing and writing songs. She said:
For me, the process was basically, I work out the movie. I'll act it out, I'll have the dialogue already in my head ... I can't be bothered to learn Final Draft. ... Like, when I sing, I just want to sing the melody and write the lyrics. I don't want to have to do production, which is very technical. I don't enjoy that.
The project, originally conceived as a non-musical film, was subsequently written as a musical, with songs by Sia and choreography by Sia's frequent collaborator Ryan Heffington. It was first given the working title Sister and subsequently renamed Music. By 2018, Kate Hudson and Leslie Odom Jr. were also set to star.
Sia stated in 2019 that the film was set for release in October of that year, but it is now due for release in IMAX theatres on August 22, 2020.
Sia wrote 10 songs for the film; she released "Together" as the lead single from the soundtrack on May 20, 2020.