Dissonance

Dissonance is the perceptual quality of tension, roughness, or instability in a combination of simultaneous pitches. In Western tonal practice, dissonance creates the drive toward resolution — the expectation that tension will give way to consonance. Without dissonance, tonal music would have no motion; it is the engine of harmonic movement.

Like consonance, dissonance is not a fixed property of intervals but a culturally and contextually shaped perception. What sounds dissonant depends on what the listener expects, and expectations are trained by exposure to particular musical systems. The history of Western music can be read as a progressive expansion of the boundary between consonance and dissonance: intervals that sounded harsh in one century became unremarkable in the next.

Dissonance has also been theorized beyond acoustics. In social and political contexts, “dissonance” names the friction between incompatible positions — a usage that borrows its force from the musical experience of tension demanding resolution. Whether this metaphor illuminates or distorts depends on whether one assumes, as Western tonal practice does, that dissonance must resolve — or whether, as many musical traditions demonstrate, sustained dissonance can be a stable condition rather than a problem.

Related terms

• Consonance — the complementary quality of rest
• Harmony — the domain in which dissonance operates
• Tonality — the system that assigns functional meaning to dissonance