Just a clarification on 4'33": recordings of it are not pure silence (and are not intended to be). They're recordings of actual musicians on an actual stage, no

Just a clarification on 4'33": recordings of it are not pure silence (and are not intended to be). They're recordings of actual musicians on an actual stage, not playing any music. So you hear lots of little environment sounds, movements, coughs, etc. It seems plausible for a particular recording of that piece to be copyrighted. Or for the instructions to be. The issue in that link is weird because it seems like part of the problem is that he credited Cage on his own album, admitting that he was copying it.