Harmony is the simultaneous sounding of different pitches and the way those combinations move from one to another. In Western music the most familiar harmonic language is built on triads and seventh chords that create patterns of tension and resolution.

A melody can stand alone, yet harmony gives it context and emotional direction. Chord progressions guide the listener’s expectations. Composers and songwriters choose harmonies to support, color, or sometimes deliberately contradict the melodic line.

Different styles treat harmony differently. Classical common-practice harmony follows relatively strict rules of voice leading. Jazz expands the palette with extended and altered chords. Some twentieth-century and non-Western traditions use other organizing principles altogether. Studying harmony trains the ear to hear relationships that lie beneath the surface of the music.

Even simple songs gain depth when the harmony moves with intention.