Historically, 27 can be a fraught age for a musician. For Finneas O’Connell, it’s been a triumph.

In May the album he produced and co-wrote for his younger sister, Billie Eilish, HIT ME HARD AND SOFT, debuted as her best-performing LP yet, eventually racking up over 1 billion streams on Spotify and spawning one of the songs of the year, “BIRDS OF A FEATHER.” A few months later, he released his second solo album, For Cryin’ Out Loud!, and kicked off a world tour with his band. He also found time to score the acclaimed Alfonso Cuarón Apple+ series, Disclaimer, as well as land an acting role in the upcoming Peacock comedy Laid. And in February he’ll join Eilish at a ringside table at the Grammy Awards, where they have become fixtures this decade, winning a combined 19 trophies, including last year’s Song of the Year prize for Barbie’s “What Was I Made For?” This year, Billie is nominated for seven Grammys (including for Song, Record and Album of the Year), and FINNEAS is up for four.

The only lowlight of his 2024: doing this interview with HITS.

I saw you at the Sabrina Carpenter show at the Forum. What’d you think?

I loved it. I think she’s so great. I’ve been a fan of hers for a long time, and I remember end of 2022 getting to know her and thinking, “This person really has it.” Obviously she was already successful, but she hadn’t exploded into the phenomenon she is now. But I remember thinking, It’s probably just a matter of time. Because she has a crazy work ethic, she’s super-smart and funny and she’s really talented.

What was your takeaway from the show itself?

So thoughtful, so theatrical. It was like going to see something on Broadway. It was awesome.

Thinking about the state of pop music, tell me if you think I’m wrong about this, but it seems that the one artist/one collaborator relationship has supplanted the loads-of-songwriters-per-project approach. There’s you and Billie, Chappell Roan and Daniel Nigro, Olivia Rodrigo and Dan, Taylor Swift and Jack Antonoff. Do you think this signals a shift in the way pop is being made?

Well, Taylor also works with Aaron Dessner a lot. Sabrina works with Jack, Amy Allen, Julia Michaels, Jon Ryan and Julian Bunetta. Amy worked a little bit on Olivia’s record too, and there are writers I love on some of those Chappell Roan songs: Amy Luney co-wrote “Red Wine Supernova,” Justin Tranter co-wrote “Good Luck, Babe!”

So you’re wrong, Craig. How do you feel about being wrong, man?

I can live with that. It’s certainly not the first time.

Listen, in truth, the producer-artist pairing is in vogue, and that’s great. My personal experience is that the best results I get are from working with somebody I’m comfortable with. If I meet somebody new who I think is brilliant, I have to get to know them. I have to get comfortable enough so we can tell each other no, I don’t like that idea. Think about the times in your life that you have a dinner guest and you just feel awkward saying, “Hey, I’m tired. I need you to go home.” It feels impolite. I think of collaborative relationships a little like that. You need to be able to tell somebody, “I think we need to try something else.” And if it’s a brand-new person, I’m not going to feel the same freedom I feel with Billie, where I’m, like, “I’ve known you my whole life and I’m not crazy about this idea.”

In your salad days, did you ever do songwriter camps?

I never did a writer camp. Actually, that’s not true. Billie and I did some writing camps for the Suicide Squad movie. But I did years of songwriting sessions, every day, randomly put together with writers and artists and producers, and I’d just go in every day. I learned a lot from it and I’m grateful I did it. I don’t have the stamina for that anymore. And it is a little bit like buying lottery tickets. It usually doesn’t pay off. But sometimes it did. I actually wrote a bunch of songs with Dan in 2016.

Were you guys writing for somebody in particular?

No, we would just get in and write songs and then we’d pitch them to other people. It was really fun. Who else did I work with? I met Benny Blanco years ago and still work with him a lot. I’m sure there will be some period where I do it again, but right now I’m off on different journeys. There aren’t enough days in the year to work with everybody who’s talented in L.A.

When you and Billie write, what’s your process? What comes first, music or lyrics? Or is it song-dependent?

John Mayer calls it "Ouija-board songwriting." You sit and play something on the piano or the guitar and you pretend the song already exists, and usually it comes out, at least a few lines of it do. Barbie, great example of that. Played some chords, Billie goes, “I used to float”… It’s in your subconscious. And then you go, “Okay, well, I used to float what?” And then you go, “Now I just fall down.” Okay, “I used to know, but I’m not sure now,” right? And you come up with rhymes. But the seed is kind of already planted.

For the first time, Billie’s gone on tour without you. Was that a difficult decision for the two of you to reach?

It was a decision I made in 2022. I turned in my two-years' notice, knowing that her current tour would take a couple of years to plan. I was, like, “I think two years from now, you should build it without me, and I’ll still do all the promo. I’ll still do SNL and Fallon and Colbert and anything you want me to do, but I don’t want to be the reason you tour less.” She loves to tour, and we were seeing less and less of each other on the road.

Her show has gotten intense enough that Billie sleeps most of the day, and then she gets to the venue and she does physical therapy and she eats a clean, healthy diet that makes her feel good onstage, and so there’s not a lot of hanging out. I’d be wandering around cities totally alone all day. We’d get to the arena and I’d play Call of Duty for five hours. It was pretty unhealthy. There wasn’t a lot of camaraderie. And that’s really why I tour with her, to hang out with my sister. The thing that I feel like I’m really of service to is making the album. I’m not the best bassist or the best piano player standing 45 feet behind her onstage. So it’s, like, let’s have somebody else do that, and then while she’s on tour, I can be working on a TV show or a solo record. And then when she’s home, I can be there for her and make her albums with her and be really present.

The song “Family Feud,” on For Cryin’ Out Loud!, is clearly about your relationship with Billie. Was that a harder song to write than most on the record?

It was definitely the most personal. She’s the person I’m closest to, whom I’ve always been the closest to. And so I felt extra pressure to get it right. I really made that song for Billie. It’s in second person. It’s to her. It’s not really about her; it’s to her. So if I had played it for her and she’d been, like, “Yeah, I’m not crazy about this,” I probably would’ve just not put it out.

I assume she liked it.

Yeah, she was very kind about it.

When you made For Cryin’ Out Loud!, you worked with a band, whereas you more or less did everything yourself on your first album. Was that more of a sonic decision or a process decision?

It was really a fun decision. I made the first album alone. It was very lonely and isolating, and I wanted to be more collaborative this time. I had resources that I didn’t used to have, and I’m friends with musicians who play music I love. Miles Morris is a drummer I’ve been a fan of since I was in high school. My other friends—Aron [Forbes], David [Marinelli], Ricky [Gourmet] and Lucy [Healy]—are phenomenal musicians too. And so I was, like, “Wow, this is going to make me so inspired.” And I was right. It was so inspiring. And live, it’s so much more fun than being up there alone.

You did the score for the Alfonso Cuarón series Disclaimer. What did you learn about yourself?

That I could do it. I was, like, “I guess I can actually score a TV show.” When I got the offer, I thought, Oh man, they’re going to find out I can’t do it. It was a really exciting, stressful period of time, but I’m really happy about how it turned out.

Is the deadline intense on something like that?

There are so many deadlines. You have to be turning in so many pieces of music so quickly to meet all their deadlines. It’s really crazy.

Is the director sending you footage and you’re writing to a scene, or is he sending you an idea? Like, “People are going to be snogging; write a song for that.”

I read the script and I wrote some pieces of music, but mainly you write to picture.

You’re typically the auteur or co-auteur on a project. Was it strange getting a bunch of notes from someone?

Billie gives me tons of notes, so I was very prepared for it. I knew going into it that’s what I was signing up for. Usually it makes it better. You send in something and the director goes, “I’m not crazy about it. Here’s why.” And you go, “Okay,” and you make another version and it gets better. There were a couple pieces where I’d get no notes and I’d almost second-guess them. I’d be, like, “Are you sure? I can try again.”

Did you try any instrumentation that you normally don’t work with?

Oh yeah. I didn’t really know anything about string quartets, so I had to learn a bunch about composing for a string quartet and the different registers of the viola and the violin and the cello, and how to have them have interplay and how to have them trade off lead line. It was like going to college for classical music.

How’d you learn that?

A lot of it was just sort of mindful listening, listening to great string quartets and hearing what was actually going on. And then David Campbell, who helped us notate, taught me a lot about it, because he’s a real expert.

You’re also in an upcoming Peacock comedy series, Laid. I know you’ve dabbled in acting in the past. Is that something you’d like to do more of?

I love acting. I don’t really have much time to do it, so I have to be careful about anything I get involved in. But in this case, I really liked [Laid star] Stephanie Hsu, and it was a short ask. Literally days, not months of time in Appalachia or something. It was really fun.

One final half-baked theory to run by you. Some of the best pop music of 2024—Billie and Chappell and Charli, to name three artists—serves as a small resistance movement against Trump and bro culture. Pop has always been feminist- and queer-coded, but this year explicitly so, and it’s making a political statement, intentional or not.

That’s cool. I mean, Billie continues to be authentically herself, and sometimes that can be... I don’t want to speak for her, but putting out a song like “LUNCH”…

It’s a very vulnerable thing to do.

Absolutely. But I always think that means you’re putting out the right thing.

Photo credits (in descending order): Muriel Margaret (preview, 1), Shervin Lainez (2, 5), Henry Hwu (3, 4)