It can do this transparently, or with the ‘Cher/T-Pain’-style sudden jumps in pitch for which it became infamous, depending on how it’s set up.
In the simplest terms, Auto-Tune Pro - like all Auto-Tunes before it - takes an incoming monophonic signal (vocals are the primary target) and automatically corrects any wayward pitching within it - ie, it puts your out-of-tune singer in tune. However, we didn’t review Auto-Tune 8, so here we’ll take in the plugin as a whole, and point out the new additions as they come up. Considering that’s a three-year development period, the amount of new features added for the latest and greatest is actually rather meagre.
The new version, Auto-Tune Pro, replaces Auto-Tune 8, which was released in 2015.