I have recently modified Gordon's Enkelaar - one of the mods was to give a variable tone control rather than a switch with two tone settings.
I have added the schematic to my E14 Theremin (http://www.element-14.com/community/docs/DOC-23047/l/enkelaar-theremin-schematic) page.
Personally, I would not advise building this Theremin - The EPE 2008 design is much better.. but it may be worth copying the distortion / overdrive / tone bit - for such a crude simple circuit, it gives good results.
I have added the schematic to my E14 Theremin (http://www.element-14.com/community/docs/DOC-23047/l/enkelaar-theremin-schematic) page.
Personally, I would not advise building this Theremin - The EPE 2008 design is much better.. but it may be worth copying the distortion / overdrive / tone bit - for such a crude simple circuit, it gives good results.