As melody grew more complex, more fragmentary, or more vague, harmony grew more and more dissonant. The concepts of consonance and dissonance, as we noted on page 28, rest on the fact that certain combinations of pitches (consonant chords) sound stable and at rest, whereas others (dissonant chords) sound tense and need to resolve to consonant ones. In a famous phrase, Schoenberg spoke of “the emancipation of dissonance,” meaning emancipation from that need to resolve. Dissonance was to be free from the rule that says it must always be followed by the appropriate consonance.

Tonality, as we know, is the feeling of centrality, focus, or homing toward a particular pitch that we get from simple tunes and much other music. As melody grew more complex and harmony grew more dissonant, tonality grew more indistinct. Finally, some music reached a point at which no tonal center could be detected at all. This is atonal music.

Melody, harmony, tonality: All are closely related. Beleaguered conservatives around 1900 referred to them jokingly as the “holy trinity” of music. The “emancipation” of melody, harmony, and tonality all went together. This joint emancipation counts as the central style characteristic of the first phase of twentieth-century avant-garde music.