Wozzeck is generally regarded as the first opera produced in the 20th-century avant-garde style and is also one of the most famous examples of atonality (music that avoids establishing a key) and Sprechgesang. Berg was following in the footsteps of his teacher, Schoenberg, by using free atonality to express emotions and even the thought processes of the characters on the stage. The expression of madness and alienation was amplified with atonal music.
