You can see it next to his Prophet T8.

In a session picture shared by The Weeknd's producing and engineering team, an Oberheim Matrix 12 synthesizer is clearly visible at the bottom of the rack in the background.

Used on Perfect Machine, as specified in Herbie Hancock’s Electronic Instrument Glossary from September 14, 2016.

Oberheim Matrix 12 – Released in 1984, this polyphonic analog synthesizer is known for producing one of the best sounds available. It has an ability to produce an almost limitless variety of sounds. This was used on Herbie’s 1988 album Perfect Machine.

This Sound On Sound article states that Emerson owned an Oberheim Matrix 12.

He is seen using the desktop module version of the Matrix 12 by Oberheim. You can tell its not the keyboard by the metal work on the bottom of the synth.

This tweet from Morris regarding the recording of New Order's Music Complete album states that he owns a Matrix 12, although he doesn't seem to have played it on the record.

"As for hardware synths, Rjd2’s Clavia Nord Lead Electro, Korg Polysix, Yamaha CS-80 and SY-2, ARP Pro Soloist, and Moog Minimoog provide color to his beat-pulsing tunes. The “synth room” holds an ARP 2600, Moog Polymoog, Sequential Circuits Prophet 5 and Prophet T8, Rhodes Chroma, Oberheim Matrix 12 and Oberheim OB-Xa, Roland Juno-60, Elka Rhapsody 490 String Machine, and Elka Synthex."

Used on their 1982 tour. Can be seen on the Oil on Canvas video.

According to Keyboard magazine August 1995 issue (translated into French), the Matrix 12 was one of the synths used by Steve Porcaro on Michael Jackson’s HIStory album.

"What do you remember of the hardware setup you had in the early days?

Andy: We had an 808, 303, 202 and 101, a monophonic digital synth, Akai 950 sampler and a few other analogue keyboards. We hired in an Akai S1000 to record the first EP.

Ed: Also the Oberheim Matrix 12 and Matrix 1000, which were pretty important. Sequencing was initially an Alesis MMT-8 then Dr T’s on Commodore."

In the interview "Watermark recording process". The Music Magazine (Australia) July/August 1989

THE SET UP:

They use a variety of keyboards but the mainstays are a Yamaha KX88master Yamaha DX7 Emulator 111 Oberheim Matrix synths and Akai S900 but particularly Roland's D50 and Juno 60.

Enya: "The Juno is one of our favorites. We had intended to replace its parts with better sounds but we couldn't find better substitutes so we left them in. It's not always possible to have all the sounds I want for a song at the time of composing .I'd usually start with the D50. But most often, sounds suggest parts and the ones I use then are usually used on the final recording. Like on Storms in Africa... that arpeggiated line on the Juno 60 was the basis of the piece."

Jens Johansson discusses his use of the Oberheim Matrix 12 on his Panix page. He describes it as one of the greatest synthesizers ever built, despite some design flaws like the internal control signal sampling rate. Johansson appreciates its warm, rich sound for creating pads, noting that it is unmatched by other synthesizers. However, he mentions its sensitivity to misuse and contrasts it with his experience using the Oberheim M6/M1000, which he finds more reliable due to its simpler design and architecture.