Robot voice or sound modulator circuit

The demo starts at 4:05 . I remember when I was 17, I often visited an electronics store - not like the ones we have today where they sell computers and kitchen appliances but one where they sold components and tools for making your own constructions. They had a rack with kits and one of those where labeled “roboterstimme“ which is German for robot voice. I never bought it but some years later I found a schematic that probably was for the aforementioned kit. I have now made my own version of it based on the schematic and this is what this video is about. The music is something I put together myself using my Wersi Prisma organ and a small Bontempi keyboard for the rhythm.