Okay, granted, this was back in October and I am just now running across it.
According to my preliminary Google search, the organ at Wanamakers department store is believed to be the largest pipe organ in the world [28,000 pipes] and quite possible the largest 'playable' musical instrument in the world. Watch what happens when unsuspecting shoppers are treated to a surprise concert from members of the Philadelphia Opera Company.
How cool is this?
And if you want information on the event, here's the article from the Philadelphia newspaper...
Flash Opera Hits Macy's