[sdiy] Synthesizer for childs?

[Tim Escobedo]

One neat cheap trick I've tried a couple times now has been to use a
joystick such that the X axis controls oscillator pitch and Y axis
controls pulse width (and volume). The simplest implementation used a
hex Schmitt trigger. One Schmitt trigger used as a oscillator which
feeds a second as a buffer, which goes through a variable RC network (Y
axis) feeding the third Schmitt trigger. The RC network gives a
variable pulse width from 0% to over 50% depending on the frequency.
Simple one chip construction, easy on batteries. I've used a 74HC14 run
off two AA batteries. It's probably not difficult to use one axis as a
VC source and use a 4046 VCO and the built-in ex-or to do the same job.
It might also be neat to add a simple bridged T filter to get some
resonant sounds, even hacked into a simple VCF.

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