This is an adaptation of an effect called Push Me Pull You from Tim Escobedo. The name says it all, two transitors operating in Push-Pull. The sound is really nasty! If you want to lower your sustain and get some octave, this one is for you! I guess it would be great for organ. You can have a look on his genius designs over at Circuit Snippets.
The PCB is single sided, easier to make and sufficient for this application.
The source .brd and .sch files along with a .pdf export are available at: http://www.sendspace.com/file/fnsh03
Little sound preview from the original