Demeter Tremulator

Here's a great sounding tremolo circuit from Demeter–the Tremulator. It's an optical trem, using a VTL5C1. That part can be replaced with an LED and a LDR (600Ω on/50M off) combo. Also, the diodes used in the originals are 1N5229 4.3v zenners, though you can use other zenners up to 5.1v. Here's the schematic for reference.