see the help patch to get an idea: menu: Help -> Library -> Community -> tiar -> filter ->APChain
Still under development.
This is a nested chain of first order all pass filters.
These are all pass filters, whatever the settings, all frequencies passes through it, no kidding.
But, it changes the phases on certain frequencies.
By modulating its characteristic frequency and its nest feedback g2 coefficient it is possible to create sorts of vibratos/chorus as found on some early analogue organs.
By mixing it's output with the incoming signal, it is possible to recreate the famous phasing effect.
The help patch implements such a phasing effect with a 3 octave paraphonic string sound and a little reverb like it is 1978.
Here it is used first as a fast modulation "vibrato", second as the classic deep and slow phasing: