I made a VOS (Voice of Saturn) synth a few months ago.
It uses a 555 timer and a 556 dual timer to generate the sound, modulation, and the LFO.
It’s a great little device.
I packaged it into an old medical supplies box and painted the top.
You can find the schematics and kits at http://www.curiousinventor.com/.
They have a lot of really cool stuff and it’s all open source!