Freddie Mercury

In this photo from Mountain Studios, Freddie Mercury can be seen recording with an Oberheim OB-Xa synthesizer. The photo was most likely taken during sessions for The Works by Queen, rather than Hot Space (which is all Jupiter-8 according to Reinhold Mack, no Oberheim).

Freddie once owned one of these however was unhappy with it, choosing to let John Deacon take it who would go on to write You're My Best Friend on it. Freddie also used the Wurlitzer at a single concert as he didn't have a piano at the time and the Wurlitzer was all the venue had (see photo).

Freddie mercury plays a korg M1 with the sound "ooh ahh"

In the One Vision and A Kind Of Magic Sessions, you can see what is clearly a Jupiter-8 but with the brand labels taped over for whatever reason. The arpeggio bass at 4:24 in One Vision was done on the Jupiter as that is the only synth they had available to have an on board arpeggiator.

Queen began using the Fairlight CMI starting in the 1984 album The Works. Freddie Mercury himself used it in his solo album Mr. Bad Guy in 1985 and again in 1986 in the A Kind Of Magic sessions as seen in this 1985 recording session for One Vision

Freddie Mercury used the Yamaha DX7 during the recording sessions for Queen's album A Kind of Magic and potentially The Miracle. Many stock DX7 presets, such as Syn-Orch, E-Piano-1, and Tubular Bells, can be heard throughout the album, as evidenced by the image provided on Equipboard.

Freddie Mercury used the Sequential Circuits Prophet-5 synthesizer on his 1988 solo album Barcelona, as confirmed by Queen Songs.