Subdecay PROTEUS: Envelope and Random Sample/Hold Step Filter - YouTube
Guitar Pedal X - GPX Blog - Old Blood Noise Endeavors's ingenious Float Dual Moving Parallel Stereo Filter takes the Filter Pedal Format to new heights
Amazon.com: EarthQuaker Devices Spatial Delivery Envelope Filter Guitar Effects Pedal with Sample & Hold : Musical Instruments
Pigtronix Introduces the Resotron Analog Filter Pedal – No Treble
SIDE STEP™ - universal variable state lfo – Godlyke Distributing, Inc.