FINNEAS

At 0:19 you can see, by design, the OP-1 in a plastic case sitting on a desk.

Finneas appears to be playing a Wurlitzer 200A Electric Piano because of the music rack, alluminium faceplate and the written part on it.

The sequential Circuits Prophet XL can be visible in the background around the 00:20 timestamp in the finneas producing therefore i am: Mixing with the masters video

At around 16:05, Finneas says that his rack for live shows includes a Nord Stage 3. It is unclear whether or not he uses the 88 or 76 key version. At 16:13, he says that it's "always [on] a grand piano because it's just got such good hammer action," which is great, since Billie's songs usually include a piano.

Finneas uses it frequently on Billie Eillish performances

In a recent vlog of Claudia Sulewski, While showing the now flooded studio of Finneas. A Novation UltraNova can be seen on the top among two other synthesizers

In this video the Meletron can be seen in the back with other keyboards at 0:06 as FINNEAS talks about how he produced vocals for Billies song Therfore I Am

At the start of the video "Billie Eilish and Finneas Break Down Her Hit Song 'Bad Guy' " posted by Rolling Stones you can see the Kawai acoustic piano.

In this Interview at around 0:42 Finneas talks about how he either used a Prophet X or a M-Audio Venom for his song How It Ends on his album Optimist and he said that he's confident that it was the M-Audio Venom. He also said he got it off of eBay for a nominal amount of money

In this Interview at around 0:42 Finneas talks about how he either used a Prophet X or a M-Audio Venom for his song How It Ends on his album Optimist but then around 1:30 he talks about how he uses a Prophet X patch for the background of the song and says it sounded like seagulls or something

In the production of the song "CHIHIRO" from their album "HIT ME HARD AND SOFT," FINNEAS used the Korg MiniKorg-700s, as evidenced by production videos released on Billie Eilish’s TikTok in April 2023.