Finneas Reveals Hidden Sounds In 'Bad Guy' And Our Worldview Is Changed

Grammy winner Finneas O’Connell, aka Billie Eilish’s big brother, spilled some fun secrets on “The Tonight Show starring Jimmy Fallon” Monday. (See the video above.)

O’Connell said he and his superstar sister have taken to recording everyday sounds to expand what he called the “tool box” of material they use in their music collaborations.

Eilish, for instance, came home from an appointment for her Invisalign teeth straighteners with a recording of the high-pitched sound of a grinding device, recalled Finneas, who often goes by only his first name. The blood-curdling noise made it into the song “Bury A Friend.”

The woodpecker-like tapping of a pedestrian crosswalk warning in Australia became a rhythmic addition to the megahit “Bad Guy.”

Genius. The siblings combined last month to win 10 Grammys (some shared), so a peek into their creative process is a treat.

Hear the results and Finneas’ interview above.