digital synth CGS digitally controlled oscillator Aries Synthesizer oscillator frequency programmable

 http://synthpanel.com/

 

https://sdiy.info/wiki/CGS_digitally_controlled_oscillator 

4QD-TEC: Electronics Circuits Reference Archive Programmable Clock Oscillator
https://www.4qdtec.com/pco.html

https://www.instructables.com/Circuit-Collection-of-the-Programmable-Unijunction/