this is a project i made for someone. i wasn't so happy to build it as the concept wasn't fully working, but it was in exchange for a usb cart which gave birth to my usb gameboy camera so its ok.
what does it do? well it takes clock pulses from the gameboy and uses them to interrupt the audio or change the pitch of the gameboy in time with the music. the dials at the bottom control the pitch, duty cycle and multiplier.
here are the YOUTUBE videos of it working:
self pitch sync:
http://www.youtube.com/watch?v=eSVOv3ZSeAA
self audio sync:
http://www.youtube.com/watch?v=nClRRK4yKT4
self pitch sync 2:
http://www.youtube.com/watch?v=k4xGP3YDbtk
two gameboy sync:
http://www.youtube.com/watch?v=nqAJX3ME0yA
here it is with the first two dials fitted
tight fit!!!
getting the arduino in and all wired up, it failed to work SOOO many times
finally got it to boot with the pitch sync
finally put it all together
have you seen my midi enabled SP yet? 
