Yielding autotune

Reading "The Yield" by Tara June Winch and find myself wondering what box could give this effect:

"There was a box taped to the mouthpiece and her voice came out in autotune." 

The book itself is enjoyable for including history from the corner of the Riverina where I've been living in the last decade, particularly the Warangesda Mission in nearby Darlington Point.