I'm not sure i understand: if the cello is delayed so I can feel like I play my trumpet in sync, then the cello player can't also feel he'd in sync with the trumpet, he must be ahead.
So there is some sort of hierarchy of instruments or a dumb sync track pre-recorded.
I'm not a musician, but I interpreted it like this:
Lets say the delay is 15 seconds, you hear the composite, including your part delayed, and you "think, cool, I played the right thing at the right time, I'll keep going with my same assumptions" or you hear "my part was way off, but the rest sounded decent enough, better do something different."
The part where everyone is just playing terribly isn't a concern or doesn't manifest because you've got a bunch of intermediate or better musicians playing.
You're right, but most speakerphones still aren't even properly full duplex, much less utopian zoom software for apex cyber virtual orchestras.
The amount of times I'm tripping up on my own words because the last thing I said is blaring out a friends/family mobile speakerphone and then back into the mic is disappointing on all levels, to say the least.
I think it works only if everyone is playing the same chord/scale. Kinda like someone playing with a loop pedal. You're right that it definitely wouldn't work with a piece of music.
So there is some sort of hierarchy of instruments or a dumb sync track pre-recorded.