this is my arduino based sync thing. it can basically sync just about anything to anything else.
it can sync anything that can make a tempo, either from midi or just from sound, or in this case the sync clock from LSDJ on my gameboy,
and then it can use that to effect something else, either by changing the speed of the internal clock, or interrupting the audio stream.
it has various controls that can control the timing and duty cycle as well as the rise and fall of the wave form.
the grey gameboy is modifying the CPU timing in the black gameboy based on the clock output from LSDJ, it controls the rise and fall in the wave form. the black gameboy has been setup just to create a drone sound.