John Milton Cage Jr. (September 5, 1912 – August 12, 1992) was an American composer. A pioneer of chance music, electronic music an non-standard use of musical instruments, Cage was one of the leading figures of the post-war avant-garde and, in the opinion of many, the most influential American composer of the 20th century. He was also instrumental in the development of modern dance, mostly through his association with choreographer Merce Cunningham, who was also Cage's romantic partner for the most part of the latter's life.