When Billie Eilish sat down with her bro Finneas O’Connell for an Apple Music showcase, they blew fans away with one of their most intimate performances yet on their hit “Birds of a Feather.” The siblings changed up the song from its original synthpop vibe to a one guitar, two voice arrangement, which was just perfect for the simple love song. Eilish noted in a croaky voice that she had just returned from tour and was sick, but once she started singing, you sure couldn’t tell because she just sang like a bird.
O’Connell provided a catchy and creative musical arrangement on his acoustic guitar before singing together with his sis in the chorus. We all know about Eilish’s mercurial star power and incredible voice, but The Music Man has to say that one of her secret weapons is definitely how amazing she and her brother sound when singing in harmony together. When put together with the duo’s superb songwriting, it’s no secret as to why she’s one of the biggest pop stars on the planet right now.
Eilish performed the duet on “Birds of a Feather” for Apple Music’s Artist of the Year showcase, and the clip hit 2.7 million views when she uploaded it to YouTube on December 18, 2024. Fans gave plenty of praise, adding comments such as “I love that Billie changes it up and doesn’t sing the song exactly the same every time, but doesn’t change it so much that you can’t sing along. She’s an angel” and “Finneas killed this. His guitar and harmonies just turned it into a whole different song. Absolutely loved it.”
Eilish and her big brother have hit a real purple patch recently. The pair scored another hit live cut when they performed “Wildflower” at the iHeartRadio Music Awards in March 2025. This song is also cut from Eilish’s 2024 album Hit Me Hard and Soft, but the brooding folk-pop number showcases a very different side to her than the giddy romance of “Birds of a Feather.” Nonetheless, there were still plenty of exquisite dual vocal parts from Eilish and O’Connell, with the bridge at 2:20 being a particular highlight.
Eilish and O’Connell co-wrote “Birds of a Feather” for inclusion on her third studio album Hit Me Hard and Soft. The song found Eilish pushing her boundaries as a vocalist, as she told Apple Music that the ad-libbed “’Til the day that I die” that closes the song was “the highest I’ve ever belted in my life. I’m so proud of that.”