Three Nandhoppers, in reverse chronological order:
3 One oscillator drives three others that feed back into each other indirectly.
2 Four independent oscillators mixed into left/right in pairs.
1 The original Nandhopper, which used an improvised layout I can't really reverse engineer.
Make one of your own: instructables.com/id/Nandhopper_1_Bit_Noise_Synth/
Or listen to some longer improvisations: