Avant-garde music

Avant-garde music, or experimental music, is a type of music that is meant to push the boundaries of "what music is." It started in the 1940s and 1950s after World War II. Some famous avant-garde composers were John Cage, Karlheinz Stockhausen, and Henry Cowell.
Examples of avant-garde songs.
4' 33".
This was a song written by John Cage that is 4 minutes and 33 seconds of complete silence. It is meant to make the audience listen to the sounds around them.
Revolution 9.
This is a song by the popular English rock band The Beatles. It appeared on their album "The Beatles", also known as "The White Album" (released in 1968.) "Revolution 9" is over 8 minutes of random sounds, and someone repeatedly saying "number 9...number 9...number 9...number 9..." It was mostly the work of John Lennon and his wife, Yoko Ono.
Hey Foxymophandlemama, That's Me.
This is a song by the American grunge band Pearl Jam. It is the last song on their third album "Vitalogy", released in 1994. It is over seven minutes long. It is made up of conversations between mental patients in asylums, and psychiatrists, with distorted bass guitar and drums laid over them.