Harmony in music refers to the combination of different musical notes played or sung simultaneously to create a pleasing sound. It adds depth and richness to music, enhancing the emotional impact of a piece. Harmony typically involves chords, which are groups of notes played together, and can be classified into:

1. Consonance: Combinations of notes that sound stable and pleasant.
2. Dissonance: Combinations that create tension or a sense of instability, often resolved by moving to consonant harmony.

Harmony can be simple, like a single chord accompanying a melody, or complex, involving multiple layers and progressions. It’s essential in creating musical structure and progression, contributing to the overall experience of a composition.