Yodeling DIY? Extreme PWM/BlueBox

[johnadon]

I've been looking for something a bit different to try out, and I'm wondering if there's a DIY project that might fill this bill:

Quite awhile back I made a PWM (Escobido http://www.geocities.com/tpe123/folkurban/fuzz/snippets.html ) and depending on how I drove the Schmitt trigger with the 386, I could occasionally achieve a yodeling effect, e.g. jumpy octaves and sometimes even a 5th popping in and out. I think I was putting an electrolytic cap between the 386 and the Schmitt trigger to achieve this or maybe electrolytic caps in the feedback loop of the 386. Every once in awhile my BlueBox does this as well, especially when I drive it with an Ampeg Scrambler or Foxx Tone Machine. I'm wondering if there are any DIY effects that take this yodeling effect to an extreme? In my mind I'm thinking of something that's sort of an almost-controllable noisemaker. I tried to get the PWM to do this consistently but was plagued by slow ticking oscillations in the circuit whenever I got (in)decent yodeling effects.

I tried searching the forums here, but amazingly 'yodeling' and other similar terms don't turn up very many hits here. And Google pointed me towards things I'd rather not even know about.....