Have you ever wanted to change your voice pitch in realtime with almost no lag? Sure there's software to do this on your phone and computer, but what about one of these Arduino thingies? 
Well, we start this project by exploring how realtime reitching works:

 And then once we have that working, we look into adding a form of AutoTune.  The AutoTune algorithm works by identifying the pitch of the audio it hears and then uses the repitch algorithm to correct it to the nearest note: