I found this article and video at mental_floss. It’s fascinating and  delightful.

Bobby McFerrin Makes a Keyboard…Out of People

by Chris Higgins – November 19, 2009

“On June 12, 2009, vocalist Bobby McFerrin participated in a panel discussion called “Notes & Neurons: In Search of a Common Chorus” at the World Science Festival. As part of the discussion, he performed an amazing feat — he trained an audience, in mere seconds, to become a sort of human keyboard.” http://www.mentalfloss.com/blogs/archives/41186