How did Arnold Schoenberg’s atonality depart from traditional tonality?

Arnold Schoenberg’s departure from traditional tonality marked a fundamental shift in Western music by abandoning the hierarchical system of a central key or tonic.12

In traditional tonal music, melodies and chords are organized to create patterns of tension and resolution relative to a central pitch. Schoenberg, building on the increasingly complex chromaticism of the late 19th century, began composing works around 1908 that consistently avoided establishing such a tonal center. This "free atonality" relied on alternative structural elements—such as recurring motives, rhythm, texture, and interval relationships—to provide coherence in the absence of functional harmony.123

Schoenberg later formalized this departure through the 12-tone method, a system where all 12 pitches of the chromatic scale are treated as equal, "related only to one another," rather than prioritizing specific notes as focal points. By removing the traditional hierarchy of keys, Schoenberg provided composers with new frameworks for musical expression and organization that challenged centuries of established convention.142