the car, the fuzztone …
Simple hack turns RaspPi into an FM transmitter with a 100 meter range. Broadcast your favorite music throughout your house, dorm, or football field.
Powered computer speaker feeding back into itself. Homebrew tremolo, oscillators. Cheepo Karaoke machine.
Monotron, feedback loop via mini FM transmitter, Barbie Sputnik, homebrew oscillators into cheepo Karaoke machine, Fisher-Price toy radio.
A more free range attempt at reading a map using several passes of a DIY oscillator driving a raw speaker with various stuff cradled in it.
Iterations of homebrew oscillator, finagled by hand and/or yet another homebrew oscillator.