I was disappointed when I found out Jarre didn't use a Moog on Oxygene. So now does this mean he did use a Moog and even a theremin as well?
In those days there was no sampling to speak of so you had to set up the dials and connect wires to plugs, record yourself playing all the notes for ONE instrument sound, then take it all apart and do the next sound. When you were done you assembled it all in editing. Here's Jarre's ancient synthesizers in action:
Those Moogs are probably the least awesome things in that room. I got to play around with one of those EMS suitcase synths and it's a wonder anyone can make music with them.
What you say about sampling, by the way, could be said about a guitar or drums or whatever. You need people to either physically sit there and play them live, or record them. In fact he demos an old sequencer here that would totally allow you to Jam with yourself real time.