i've convinced myself that what was broken in the drivers was the separation of the tracks. the more i explore this, the more likely it is that it's going to start looking random.
i can't verify that cubase processes individual tracks before it mixes them, but it seems like an unavoidable conclusion.
it would then have to be that it broke at the mixing stage - that the tracks were corrupted as they were being combined, on a stream-by-stream basis.
this should be at the driver level, because it's what drivers do: they act between hardware and software instructions.
i'm still a little unclear on exactly how this works, but the inference is that the hardware must be streaming the individual parts separately; that the "mixing" isn't actually done in hardware, but in the listener's ears. like an rgb gun, or a computer monitor for that matter - it shoots out the different colours independently and allows the result to exist in observation. there's no violet inside your computer. there's only instructions on how to create violet on your screen.
if i can verify that this is true, i'll be convinced.
but, i don't think it's going to help a lot in reconstructing it. it means i'd have to run independent processes on each of the tracks, because the corruption is happening on the other side of the master effects.
so, today wasn't a loss. i feel i finally *understand* what's happening. that should help me put it behind me and move on.
talk about a weird error, though. no wonder i couldn't figure it out.
to keep to the colour analogy, i guess it would be sort of like that i had a dirty printer head, and i was getting splotches on the paper as a consequence of it - those splotches being strange frequency boosts.