Yeah, you have to know something about how he used to play the CS-80. He didn't rely on envelopes to do all the "slow fading" work, he used the volume pedal actively. Also a heavy user of the aftertouch. He said in an interview that he plays with his entire body, not just fingers. (Sounds kind of nasty, doesn't it?).
The CS-80 has a unique kind of aftertouch, polyphonic AT. It means that every key has an AT sensor underneath, so you can accent single notes in a chord by pressing the key harder than the others. On a regular AT keyboard, all notes get accented when you press one key harder. Poly AT keyboards are extremely uncommon, I believe it's only included in a couple of synths, like the Ensoniq SQ-80. The SQ-80 is weird to play on, the poly AT uses a metal bar below the keys, so the keys constantly slam into the metal bar when you play, making quite a racket

But it works amazingly well if you know what to do with it. I don't think there are any MIDI keyboards at all with the Poly AT feature?
I know most of the VA synths can accept poly aftertouch via MIDI though.
Mostly Vangelis used aftertouch for vibrato and filter cutoff at the same time. More vibrato for harder pressure. You hear it in his performances. Also the full-keyboard size ribbon controller for pitch control of entire chords. That could be emulated with a usual mod wheel with high range. We tend to forget that the cs-80 is a fully functional 2-VCO synth like every other, it CAN do more than those slow brass sounds. It's just that weird vintage organ look...