Explain Auto-Tune in a simple way
when I read the original autotune patent few steps made me understand that everything was done in time domain (in the past, I don't know today), they didn't mention anything about overlap and add, it made me wonder if the pitch detector is so good that they didn't have to overlap and add, could they always skip or add periods in the exact position? (just out of curiosity I ended up implementing the pitch detector described in this patent, and honestly that's not all I imagined lol)

Take a look in the red marked piece of the patent paper:



Of course, the patent description also says nothing about keeping the formants, but to me it is clear that the above description is just a time domain method to apply time scale and change the pitch using resample.

By the way, I wrote a pure time domain "pitch correction" keeping the formants based in the papers from @robertbristow-johnson and Keith Lent 

youtube demo from my code here:

https://www.youtube.com/watch?v=6ns5K1FHtd4