Two Sides of Genghis Khan.
Here's a nice radio spot publicizing Chicago's Field Museum's Genghis Kahn exhibit. To tell both sides of the Kahn story-- the side where he's a bloodthirsty barbarian vs. the side where he was a social and political innovator-- you simply adjust the balance on your stereophonic headphones. Flip the balance all the way to the right and you hear one side of the story; all the way to the left and you hear the other. Nice example of how the medium is the message.