Billie Eilish and her brother Finneas O’Connell recently discussed their collaborative songwriting process, revealing some insights into their unique approach to creating record-breɑking debut music.

In a new video for Spotify HiFi, the Grammy award-winning siblings talked about their ‘creative space,’ with the 19-year-old singer emphasizing their need for ‘sunlight,’ a ‘good sound system,’ and ‘good base.’ O’Connell agreed, adding that they also require ‘giant loud speakers.’ Eilish stressed that high-quality audio is crucial for them because there are details that listeners can miss without a proper sound system. “It’s really important because we make music that wants to be heard the way it was made,” she explained.

O’Connell, who has been co-writing and producing music for his sister for years, reiterated that how listeners experience their music is the “most important” thing for them. Eilish responded by affirming his point, prompting her brother to mention the subtle “details” and “weird things” they incorporate into their tracks. He gave examples like background chuckling and whispering layers in their music.

In the video, Eilish wore a bright red hoodie and distressed jeans, along with her signature black hair with neon-green roots. O’Connell sported a beige button-down shirt with a jeweled collar and light blue trousers while they sat outside on a couch.

Additionally, a trailer for their upcoming documentary, The World’s A Little Blurry, released earlier this month, featured the siblings recording music at their childhood home. In one scene, Eilish was shown getting into her parents’ bed, joking with the camera crew about being afraid of monsters. Her mother, Maggie Baird, noted that she couldn’t imagine how any artist, especially a teenager, could handle the pressures of the music industry without a supportive parent.

Directed by R.J. Cutler, the documentary is described as a coming-of-age story that explores Eilish’s journey to global stardom at age 17, documenting her time on the road and at home, where she recorded her debut album. The World’s A Little Blurry is set for release in U.S. cinemas and will premiere globally on Apple TV+ on February 26, 2021.