The “music” of silence

Is John Cage’s 4’33” music? If not, what about the silences (“rests”) in the middle of a song? Here’s an interview with Cage in which he challenges common assumptions about music.  An interesting contrast to the definition I proposed–“music is the art of organizing sound in time”–is made by him here: “If music is the “enjoyment” of “sound”, then it must center on not just the side making the sound, but the side listening. In fact, really it is listening that is music. As we savor the sound of rain, music is being created within us.”
–“In this time,” http://www.livingworld.net/shop/john-cage/