Each of these words refers to musical sound. Harmony is the study of the structure and relation of musical chords, that is, the blending or mingling of sounds. Melody is the rhythmical relation of successive sounds that combine to make a tune. A tune is a series of sounds forming an air. Harmony and melody are two of three basic elements of most Western music (the third element is rhythm). Examples: "In this orchestra there is complete harmony between the brass section and the violins." "Gene sang a tuneful melody while he showered." "The only tune he could play was 'On, Wisconsin. '" The adjectives melodious and tuneful are synonymous in their meaning of "forming a pleasing succession of sounds," "agreeable to hear."
Dictionary of problem words and expressions. Harry Shaw. 1975.