John Milton Cage , Jr. usually known as just John Cage , ( born September 5 , 1912 , died August 12 , 1992 ) was a composer of Scottish ancestry . John Milton Cage Jr. ( September 5 , 1912 â `` August 12 , 1992 ) was an American composer , philosopher , poet , music theorist , artist , printmaker , and amateur mycologist and mushroom collector .