I found this project in the US magazine Popular Electronics, February 1981. Here is the link to the document: Unimod-Sound-Effects-Generator.pdf.
I was interested in how this effect sounds and after finishing it, I can only say it sounds interesting.
The power supply for this effect unit is +9/-9 Volt. But I didn’t want to feed +9/-9 volts and I first tried a small circuit with a switching voltage regulator that generates +9 and -9 volts from +12 volts, but I omitted the 5 Volt part.
But as it is then, you sometimes find other ideas as well.
This is a much simpler circuit and absolutely sufficient. Now I only have an input voltage of 9 Volt. The ExpressPCB file, with the ICL7660S, can be downloaded heer.