Aspen Times columnist Barry Smith dregs up the old story of John Cage’s estate’s successful suing over the licensing rights to 4’33”. As Smith says,
It’s more complex than that, of course, but let’s not get bogged down in legalities.
Damn right it’s more complex than Smith’s version, but no need for bogging down, it’s pretty straightforward really. So, one last time: Cage’s estate rightfully sued because the hapless Mike Batt gave a shared credit to Cage in the silent recording he used on his CD, Classical Graffiti. By his own admission, then, he was piggy-backing off Cage’s intellectual property. IP is protected by law, and if you go around using it without permission, you are liable. If Batt had claimed full credit for his silent work (as Sonic Youth, György Kurtág and others have variously done) he would have been fine. If he’d called it ‘Hommage to John Cage’ he would have been fine. But by adding Cage’s name as joint composer he was, in essence, releasing an unlicensed cover version of a work under copyright, so sorry.
That clear now? Good.
The Rambler 
Just to add to the list of silent composers, Cage’s sometime neighbours John Lennon and Yoko Ono recorded two different silent pieces of their own composition, as I recall.