Years back, Sia was tasked with the opportunity to step out of her comfort zone and pen a screenplay based on a one-page story that she wrote in 2007. It ended up becoming one of the most challenging projects of her career.

Music, an upcoming musical featuring Kate Hudson, Maddie Ziegler and Leslie Odom Jr., hits IMAX theaters on August 22 and sees the Aussie pop star unravel the story of an autistic teenager, who is cared for by her sober, drug-dealing sister. "This was a terrible idea, but I'm really, really glad I did it because I think it's the best thing I've done even though it's the hardest," Sia told iHeartRadio of working on the film as a director and producer, emphasizing its harsh contrast from her usual responsibilities as a songwriter.

While Ziegler's remained a go-to for the pop star since her 2014 video for "Chandelier" and it doesn't seem like much has changed when it comes to their working relationship. "She's just become more and more talented and more and more professional and more and more skilled and I guess, so have I," she explained. "We've grown together over the last six years. There's nothing too different. I can just curse around her now."

To jumpstart the 10-song soundtrack for Music, Sia recently unleashed a self-love anthem titled "Together," which was written and recorded four years ago as part of the long-awaited film. The song, which was co-produced by Jack Antonoff and Jesse Shatkin, also serves as the closing number to the film and Sia has a particular reason for its placement. "This felt like the perfect song to end the movie because I felt like I had broken your heart and put it back together and this was the perfect song to walk out of the cinema," she explained.

As for how quarantine has impacted the star's creativity, Sia said it hasn't made an impact at all as she's making music as usual, courtesy of technology and some helpful hands. "Most of the music I make is via the internet anyways," she confessed. "I usually just record it in my closet over tracks that people send me or right now during the pandemic, I'm actually quarantined with a bunch of people I love, one of whom is an amazing Australian musician, who is recording [this interview] and everything else that I need to do while I'm here, so I'm a lucky ducky."