'I asked my music-history class the question, "What is music?" I introduced the subject by showing a video of American composer John Cage describing his silent piano composition, 4'33'' - so named because it was four minutes and 33 seconds long. After composing it, he erased the notes from his score as a way of compelling others to think critically about what they consider "music".
I was amused by one student's submission. She wrote a five-page essay, and then erased every word with white-out.'
P. Janson, Reader's Digest, Campus Comedy, Dec 1997