O, got you, definitely, could be something like an astable multi vibrator which is a fun discrete circuit to build, or a simple 555 timer in such a mode. Intro

O, got you, definitely, could be something like an astable multi vibrator which is a fun discrete circuit to build, or a simple 555 timer in such a mode. Introducing randomness is a good exercise tho, replacing a capacitor with a capacitive microphone would do it I suppose