The 22-year-old Grammy winner has always worked with her 27-year-old sibling, who co-writes and produces her output, but he's recently set her up with a "basic" kit at her home studio so she can learn production herself.
Speaking to Guitar.com, O'Connell said: "I've been setting up Billie's recording studio for her so she can do home production without me, because she's very good at it!"
Finneas has set up his sister Billie Eilish with a basic home studio to produce her own music. (AP PHOTO)
O'Connell setting his sister up to produce herself comes after they argued making her latest LP Hit Me Hard and Soft.
The producer is not afraid to call out his sister if he's not happy with the way their sessions are going and told her she wasn't being "authentic" or "honest".
During a recent appearance on YouTube show Hot Ones Versus, O'Connell explained: "I think the longest, biggest argument was during a period of transition in maybe both of our lives where we were just trying to be kind of honest.
"To give (Billie) credit, I was very much high and mighty about, like, 'You're not being honest or authentic enough'. So I learned a lot from being too egocentric in that process."
Eilish was also annoyed about her brother putting his bare feet on the sound desk, adding: "He's a lot of times barefoot, a lot of the times in very filthy shoes ... My face is right there (near the desk where his feet are). And actually we filmed so much in making the album that almost all the footage is his feet and then me."
Finneas O'Connell and Billie Eilish have spoken of arguments and frustrations while recording music. (AP PHOTO)
The siblings previously opened up about the challenges they encountered making the record in an interview with Apple Music 1's Zane Lowe in May, with O'Connell claiming Eilish wasn't being vulnerable enough.
He said: "I was like, 'Subject-wise, I'm not being led into what you're actually feeling, and I think that there are real guards up'."
O'Connell confessed he even reached a point when he considered walking away from music, and Eilish revealed she understood exactly how he was feeling.
She said: "It was very interesting because I saw myself in that. I was like, 'I have felt that way and you have always been the thing that keeps the ship moving, and now you feel that way. What does that mean for us? And what are we going to do?"
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