Yes, I don't think this is supposed to playback audio at all. It's a graphical thing, used to create 'scores' in the sense of lines, curves, vectors, points etc. moving in time. I guess it's the sort of thing Xenakis may have used to help him create/plot arboresences. Or something like that. And that one requires that score to be 'plugged into' something else if one wants to hear playback.