It’s a tremolo with 4 waveforms available and an optional bandpass filter.
Knob 1 : Speed – the tremolo speed
Knob 2 : Depth – the tremolo depth
Knob 3 : Wave – the progressive waveform (with the knob at 0 triangle, 1/3 sine, 2/3 square, 1 saw)
Knob 4 : Filter – the amount of a bandpass filter mixed in the signal, the cutoff frequency changes with the waveform
I’m planning to do some samples for my different patches.