A Mute Machine for Playing John Cage's "Silence"

A couple of years ago, a pianist played John Cage's 4'33 on the piano at Carnegie Hall.  All she had to do was not play a note for four minutes and thirty-three seconds.  But, she accidentally hit a note.  How great and historic to actually make a mistake with this piece!

That performance necessitated my invention of the Theremin 4'33, a mute machine but it uses batteries for the on/off light.  (You should look up Leon Theremin for fun.)