The one above the Mellotron is the Roland RD-250 piano, my main keyboard. The one above that is a Roland JX-3P, the first synthesiser I ever bought. The sequencer next to it is also a Roland, the MC-500 MK II. I bought the JX-3P in 1984, after The Big Express and it had a little sequencer in it.
I hadn't been interested in sequencers up till then, but found it a lot of fun to run the built-in sequencer and call up all kinds of patches. Bach's concertos and harpsichord music are very mathematical, with no rubato as such, so I began programming some of them into it.
I would programme about 16 bars of little semi-quaver notes and rests, then record the patch onto a track of 4-track tape. Then I'd continue programming the next 16 bars and drop in on an adjacent track immediately after, ping-ponging until I'd constructed the whole piece. Then I'd run the two tracks together and make a mono mix. That was my introduction to sequencers.
I enjoyed playing around with it so much that I knew I'd soon need something better; a year later I bought a Roland MSQ-100, very primitive by today's standards. I bought the MC-500 MK II in summer 1989. I still use it to this day and it's very Gregsy-friendly.
I experimented a lot with the Roland MSQ-100 for the string arrangement of "1000 Umbrellas" on Skylarking (1986). I tried to make it sound human and realistic, but I think the MSQ-100 was lost in Todd's studio. The place was infested with mice (laughs).