How did Arnold Schoenberg use all 12 chromatic notes in 12-tone music?

Arnold Schoenberg developed the 12-tone method to replace the traditional system of tonality, which relied on a central keynote or tonic to provide musical structure. Instead of assigning hierarchy or focus to specific notes, Schoenberg treated all 12 notes of the chromatic scale as equal.123

To organize these notes, Schoenberg utilized a "basic set," also known as a 12-tone row or series. This row serves as a foundational "backbone" for a composition, consisting of a specific, arbitrary ordering of all 12 chromatic notes. In this system, the composer must present all 12 notes of the row before any individual note can be repeated.123

By ensuring that no single note predominates, Schoenberg systematically moved away from the harmonic organization that had defined Western music for centuries. This technique, a form of serialism, allows the row to permeate the melodies, counterpoint, and harmonies of a piece, providing a new unifying principle where tones are "related only to one another".21