Tremolo is one of my favourite effects. It dates back as one of the first musical effects, either electronic or mechanical. It was the first reach at the musician adding to their sound for an interesting new edge. Tremolos interest me because a good design has its own living pulse, which must sound lively like the instrument itself.
By shining a fading light against a photo-sensitive material, this tremolo uses all analog photo-coupling to restrict and vary the output. This results in a unique and lively sound instead of an exact boring sound of using a transistor. Most optical tremolos I hear now don't do it for me though, and sound completely unnatural and lob-sounded. After a decade of development I've created this completely new, unique circuit, as my ideal tremolo sound.