Avant-garde music is the constant search for the new. John Cage invented the “prepared piano” (objects inserted between strings to alter timbre), and wrote 4'33″ (four minutes and thirty-three seconds of silence in which the hall's ambient sound becomes the music). Pierre Schaeffer in Paris created musique concrète — music from real-world noises recorded on discs (later on tape).
Other directions: aleatoric technique (chance elements in the score), graphic notation (scores as drawings), performative music (performance as theatrical act). The avant-garde redefined what a “musical work” is. In Ukraine, the 1960s avant-gardists (Hrabovsky, Silvestrov, Huba) faced pressure from the authorities but continued their experiments.
