Audiences often assume that consonance—the smooth, restful blending of tones—is the natural goal of music and that dissonance is merely an error to be avoided. Composers have long known better. A chord that clashes creates a sense of tension, an expectation that something must resolve; the pleasure of much Western music lies precisely in how that tension is prolonged, thwarted, and at last released. Remove dissonance entirely and a piece grows not more beautiful but inert, like a story without conflict. The boundary between the two is also historical rather than fixed: intervals that scandalized listeners in one century became commonplace in the next, absorbed so thoroughly that later ears could scarcely hear what had once seemed harsh. What counts as dissonance, in short, depends as much on habit as on acoustics, and its role is not to mar the music but to give its consonances their meaning.