Finneas O'Connell and his younger sister, Billie Eilish, have become household names. Recently, their collaborative work on the hit song "What Was I Made For?" from the "Barbie" movie has earned them nominations for "Record of the Year" and "Song of the Year" at the upcoming Grammy Awards.

The duo's small studio in the basement of Finneas' Los Angeles home is the birthplace of many of their songs together, including "Ocean Eyes," which went viral in 2015 and launched their careers.

Most of their songs together, including "What Was I Made For?" often come from spontaneous moments between the two in front of a piano.

"We sit here, co-piloting. The microphone that's over your shoulder. It's like a boom mic, and she'll just swing it around," Finneas said. 

"I'm fairly certain that was how we wrote 'Barbie' was, I was sitting at the piano. And she was sitting here or maybe on the couch with the mic," he said.

Director Greta Gerwig approached Eilish and Finneas for a "heart song" for Barbie's character in the film. Gerwig showed the duo 40 minutes of the film, and the pair went to work, though they later revised a part of the original song they wrote.

"We wrote the whole song in like 45 minutes with a bad, with a terrible bridge that we ended up, um,  rewriting," said Finneas.

Their melody was woven throughout the film's score, culminating in the emotional end to Barbie's journey. Their effort won Best Original Song at last weekend's Golden Globe Awards. Finneas calls seeing their music coexist with the scene of the movie "so powerful."

But not all projects were that straightforward. 

Finneas said the pair faced challenges while creating the theme for the James Bond film "No Time To Die." Working with iconic composer Hans Zimmer in London, he said they felt immense pressure to live up to the legacy of James Bond themes.

"James Bond has such an ethos and a sort of a signature thing. That if — if you fail, you really, you really fail. You really miss the mark," Finneas said. 

The result was a song that not only won critical acclaim but also earned them a Golden Globe, a Grammy and an Oscar.

Their journey began when Finneas was 18 and Eilish was 13, growing up in a musical household. Their mother, Maggie Baird, was also a songwriter.

At just 26 years old, Finneas is already an eight-time Grammy winner. He released his debut solo album "Optimist" in 2021, and is not slowing down. He's currently scoring director Alfonso Cuarón's upcoming Apple TV+ series "Disclaimer," and working on Eilish's new album, their third project together.

"I think that it's the closest I am with Billie to like total trust of anyone,"Finneas said.  "And total vulnerability. I'm sure there's something that she would be embarrassed to say in front of me, but not much."

Anthony Mason

Anthony Mason is senior culture and senior national correspondent for CBS News. He has been a frequent contributor to "CBS Sunday Morning," and is the former co-host for "CBS This Morning: Saturday" and "CBS This Morning."

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