Melody is the succession of notes that forms a recognizable tune. It is the horizontal aspect of music. Harmony is the combination of simultaneous notes that support the melody. It is the vertical aspect of music.
Melody and harmony complement each other and create a fuller, more interesting sound. A melody without harmony can be thin and bare, while harmony without melody can be dense and confusing. By combining melody and harmony, composers can create music that is beautiful, expressive, and moving.