Postmodern music

1968 studio album by the Beatles

music in which some element of the composition is left to chance, and/or some primary element of a composed work's realization is left to the determination of its performer(s)

music of the postmodern era, or that follows aesthetical and philosophical trends of postmodernism

Polystylism is the use of multiple styles or techniques in literature, art, film, or, especially, music.