What is the Wizard's special feature in 'The Wizard of Oz'?

Ventriloquism is the Wizard's special feature in "The Wizard of Oz."

Specifically, the Wizard knows how to project his voice. It is a talent that he uses in both the original 1900 book edition and the beloved 1939 movie classic. He becomes a disembodied voice in the film. But in the book he alters his voice according to how he projects himself to visitors.