Diy simple single triangle VCO VCA ADSR synthesizer
As a challenge, I have breadboarded a simple old school analog synth. Exponential triangle/square VCO, VCA and ADSR. Still need to make some source of the CV and GATE signal. Likely end up programming a MIDI to CV converter. Still needs a lot of work (especially to tweak the VCO, which only works well across two octaves). But as a proof of concept, I think good enough.