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Etymology from Wiktionary, CC BY-SA 4.0.
Today it means: Twelve-tone music, a form of composition using all twelve tones of the chromatic scale in such a way that they are equal, i.e. having no tonic, no dominant, no major key or minor keys, and no distinction between harmony and dissonance. Full definition →
Etymology from Wiktionary, CC BY-SA 4.0.