You may think it sounds crude, but pieces like these took hours of expensive mainframe (PDP-10) time. There wasn't a lot of opportunity for careful sculpting of fine details.
You could easily synthesize something like this in real time now. But not many people do, which I think is a shame.
If you can read French, there's more background here: http://brahms.ircam.fr/analyses/Stria/
I've kind of been following very loosely along with this DX7 series with some (not DX7) FM and phase modulation in my own code. If you're running Linux, you can try something like this in the WIP graph-synth branch[0] of my mb-sound Ruby app/gem (feedback welcome on the DSL syntax):
play 300.hz.pm(
0.1.hz.triangle.at(1) * tone(300.constant * 1.618) +
0.04.hz.triangle.at(1) * tone(150.constant * 1.618)
).forever
For sure, though the parent comment's video link was presumably rendered by software on a PDP-10. I've spent the last week of my spare time trying to write code to make a bass sound that reasonably approximates Lately Bass, and I'm close, but since I'm not even trying to emulate any of the quirks of the Yamaha FM synths it doesn't ever sound quite right.
It's the last part that's still really difficult, possibly even harder than it used to be. And that's even with the insane processor power we all have now.
There's an infinitely vast space of potential sounds, and an infinitely long fractal knife edge of interesting sounds, and it kind of makes sense that finding unexplored areas of that fractal edge between boring and incomprehensible gets harder over time.
https://soundcloud.com/cassilda_and_carcosa/ontologies-tape-...
TX81z is one of my favorite synths.
Equivalent today to milliseconds of processing in an Apple Lightning cable.
If you can't read French, use Google Translate. It handles this article extremely well.