Logic Noise: Sweet, Sweet Oscillator Sounds (2015)

Complete series, https://hackaday.com/series_of_posts/logic-noise/

A nice cheap (as modular synthesizers go) testbed for logic noise circuits is the AE modular format made by Tangible Waves (https://www.tangiblewaves.com/). It all operates on 0-5V, so experimenting with CMOS chips (as well as microcontrollers like Arduino Nano etc.) is easy, and there are quite a few modules available. They also have a breadboard module where you can experiment with small circuits directly on the module. I have had a blast with it (though I am by no means a musician), it was a gateway into Arduino for me.

Shipping from the manufacturer can take a long time (they are a small operation). There are a few third-party manufacturers, with more emerging. If you are in the states, Noisebug in California sells their stuff, and they ship quickly.

One chip I am personally interested in is the CD4089, a multiplier (https://www.ti.com/lit/ds/symlink/cd4089b.pdf?ts=16824136787...).