It’s time to confront ourselves with a pinnacle of modular synth techniques: Todd Barton’s Krell Patch. Inspired by Bebe and Louis Barron’s soundtrack for the 1956 sci-fi film “Forbidden Planet”, this patch revolves around a “modulation feedback”: a single LFO drives the whole patch and triggers many S&H circuits that generate random voltages, which, in turn, constantly modulate the LFO speed and shape.