4093 Drone
Back in 2015, when I first started messing around with circuits, one of my first builds was the GetLoFi Quad Oscillator Kit.
Based on the 4093 Logic IC, this stand alone noise machine has four independent oscillators, each of which can be independently tuned
to create a polyphonic drone tone or pulsing beep tones.
I added a couple rotary switches with a wide range of different capacitors to make it even more versatile.