for subtly different sounds try replacing d1 + d2 with 1n34's for fuzzy sounds , 1n4148 for more buzz , leds for more crunch or a 1n34.
the original diodes were germanium 1n270 types.
components connected by dotted lines signify modifications for click prevention (1m resistor ) and osillation (cap in feedback loop )
effect could be improved with true bypass switching .