Atonal music is liberation from the “pull” toward a tonic. In classical harmony, every note plays a role in the hierarchy of a key; in atonality, that hierarchy vanishes. All pitches become equal, and the music flows without the usual signals of “here's the beginning, here's the end.”
For a listener trained on classics, atonal music first seems chaotic; yet it has its own logic — a logic of intervals, motifs, and texture. Schoenberg's first atonal works (1908–1912) shook the musical world. Later the composer sought order within that chaos — and created dodecaphony. Atonality became the foundation of most 20th-century musical directions: serialism, the avant-garde, and electronic music.
