I’m currently composing on the extremely rare EMS Synthi 100, of which there are only 5 or so in working condition worldwide (26 were built).
I’ve been training up on it and had my first solo session with it today, so I immediately wanted to see how the OP1 would interact with it. Here’s some vids from my instagram (I’ll be posting more the next few days there). In both cases the OP1 output is plugged into the input amplifiers, which is simultaneously converted into audio and CV in two stream, so the audio is routed simply to the output amplifier via one of the eight (!) filters, while the generated CV in the first case is affecting the cutoff position of the filter. You can see me towards the end patching in the oscilloscope on the matrix board.
The second video is me live looping and syncing (no midi, just ear!) the OP1 with a generative patch on the Synthi. I got the insta caption a little wrong, but basically: the patch consisted of 6 saw waves, multed together through 2 filters (HPF and LPF), with one env generator on cycle, a second env generator affecting the LPF cutoff, and the CV generated from both env generators sent to the opposing env generator - so the output of env generator 1 would affect the attack and decay of env 2, and the output of env 2 would affect the decay of env 1. Confusing stuff. OSC 11 is functioning as an LFO that goes into the audio range, affecting the pitch of all oscillators in this patch.
The signal then goes through the reverb tank and to the output.
Both vids are pretty basic and were to test how the audio-to-CV inputs functioned, but I’ll be posting up some Synthi-only videos with high quality sound in the next few days/weeks 
would love to mess with an EMS! Cool to see it paired with an Op1. Nice instajams