Simple Square Wave VCO

This VCO circuit is being developed for a modular synth workshop. The 555 is often considered a hobbyist or beginner chip but is perfectly suited for breadboarding and teaching concepts involved in creating these modules. In addition to being a fun little instrument played with Pitch and Gate CV, audio can be fed into Pin 5 to achieve frequency modulation. In this instance, the 0.47uF capacitor can be changed for something that provides a lower frequency, such as a 2.2uF. Experiment!. This circuit can also be modified to serve as our LFO in a future workshop.