For today's Geo Quiz we wanted to know where 'The Nutcracker' ? the ballet ? was first performed in 1892. It's a center of commerce and culture that, for much of the 20th century, was called Leningrad. The answer to our quiz is St. Petersburg. Today you can find the ballet performed all around the world, from Hong Kong to the town of Ketchikan, Alaska. For today's Global Hit Marco Werman speaks with The World's Rhitu Chatterjee about the science behind Christmas music.