Yes, Cage is an odd one, but this is a bit different it seems (at least to me). The objective here seems to be "be as quiet as you can be". and they're just acheiving this with more natural sounds, but they create the sounds. I think Cage left it completely to chance most of the time.

My favorite is called "12 radios". Basically, 12 guys with radios walk in a circle around the (small) concert hall, tuning to different stations at random. I thought it was a stupid idea at first, but then I really started to wonder what it would sound like.