modular synthesizer driving cymatic waveform visualizer (experiments)

here's a short clip of some cymatics experiments driven from my modular synthesizer, the audio path is 1 VCO modulated by an LFO into a modulated resonant lowpass filter.  there seems to be a low-level intensity threshold of motion on the surface and also it only seems to respond well to low frequencies, even the midrange doesn't produce much wave motion on the surface....experiments continue...