In 1791, Joseph Haydn had a problem. Rich people in London came to his concerts, but many of them fell asleep during the slow, quiet parts. Haydn decided to teach them a lesson. He wrote his Symphony No. 94, now known as the "Surprise Symphony." The second movement starts soft and gentle. The melody is calm and sweet. Then, without warning, the entire orchestra crashes in with the loudest chord possible. Audience members reportedly jumped out of their seats. Haydn was not the only artist to use surprise as a tool. In the 1900s, French composer Erik Satie wrote a piece called "Vexations." The instructions were strange. Players had to repeat one short passage 840 times. When pianist John Cage performed it in 1963, it lasted over 18 hours. Was it a serious piece of music or an elaborate joke? Nobody is quite sure. Visual artists have played similar tricks. In 1917, Marcel Duchamp submitted a regular bathroom urinal to an art show in New York. He signed it with a fake name and called it "Fountain." The judges were furious. But Duchamp's point was that art could be anything an artist declared it to be. That idea changed the art world forever. From Haydn's crash to Duchamp's urinal, artists have used April Fools' Day thinking all year long.