I couldn't resist posting just a few more John Cage links before this space gets back to being all-Copland all the time.
John Cage prepared piano app! (so much fun!)
33 Musicians on What John Cage communicates via NPR Music. The list includes a comment from Paul de Jong of the band The Books, who have a thing or two to say about aleatoric music in one of their songs:
John Cage and John Cale share a Satie secret (thanks, Betty!)