"When I first saw this tremolo I knew I just HAD to try building one. After the usual brainstorming I hatched a plan. Of course, that plan took a very different turn a few times on the way to a working prototype. It uses a small gear motor salvaged from a Roomba vacuum to spin an eliptical wheel which wiggles the canister back and forth. When more voltage is applied the motor speeds up and so does the tremolo effect."