Dissonance

Dissonance is a term used in acoustics, music theory, and psychology. In music, dissonance refers to combinations of tones that sound unstable, tense, or clashing. It contrasts with consonance, which is judged as stable and harmonious. The perception of dissonance is partly psychoacoustic and partly cultural; what is considered dissonant depends on context, tuning system, and style.

Psychoacoustically, dissonance arises from interactions among partials in complex tones, producing beating and roughness when partials fall within close frequency proximity. Interference within the ear’s critical bandwidth makes certain intervals more dissonant than others. In Western tonal music, intervals like the minor second, major seventh, and diminished fifth are commonly heard as dissonant, and many chords containing these intervals create tension that seeks resolution to consonant sonorities. Dissonance can also be produced by rhythmic or harmonic spacing, syncopation, polyphony, and modal or tonal uncertainty.

Context and history matter. Dissonance is used deliberately to create forward motion, emotional color, and structural contrast, and its acceptance varies by era and genre. Medieval and early Renaissance practices emphasized consonance, while later periods broadened dissonance treatment with chromaticism, functional harmony, and, in the 20th century, atonality and polytonality.

In psychology, the term dissonance also refers to cognitive dissonance, the psychological discomfort experienced when holding two or more contradictory beliefs, values, or attitudes. This concept, introduced by Leon Festinger in 1957, is distinct from musical dissonance.