eventually one of the things i want to build & use is a "waveform animator". i don't know how they work, but i do know they tend to be large and expensive.
my take on the idea is a bunch of all-pass filters, but unlike a normal phaser, sweep the filters out of sync. pan to fill the stereo space nicely.
testing out the theory in software, using multiple instances of ReaEQ and Renoise's automation LFOs to simulate the effect, to see if this is even vaguely worth pursuing. i think it could be.