Interesting video that shows there is some truth to this. Also another video demonstrating auto-tune.
https://www.youtube.com/watch?v=AsQUQ8P8c-A
https://www.youtube.com/watch?v=RF67YxdCJdk
https://www.youtube.com/watch?v=AsQUQ8P8c-A
https://www.youtube.com/watch?v=RF67YxdCJdk