This is an instrument I built recently using the CD40106, a hex Schmitt trigger integrated circuit. It uses only two of the available six Schmitt triggers on the chip. While researching this chip (and a few others) I was a little overwhelmed by the possibilities so I decided to keep it simple (for now) and build something uncomplicated and fun but still challenging.
The case is made of 4 hardy cardboard panels fit into the outside wood blocks’ grooves. There’s hot glue, wood glue, and super glue in this thing. The white keys and buttons underneath were from toys. The bottom cardboard panel is attached with a single screw and has a 9V battery box (also from a toy). Here’s a picture of the back and bottom.
And this is what it sounds like!
Switches and knobs from left to right: on/off, LFO triangle or square wave, LFO rate, LFO mod amount, pitch, volume.