We are used to hearing melodies against a background of harmony. To the movement of the melody, harmony adds another dimension that is called depth. Think of harmony as occurring on a vertical plane. It is a description of the simultaneous happenings in music. Harmony is to music what perspective is to painting and drawing. The role of harmony is apparent when a singer is accompanied by a guitar or piano. The singer presents the melody while the instrument provides the harmonic background.

Harmony concerns the movement and relationship of intervals and chords. An interval may be defined as the distance, and relationship, between two tones. A series of tones arranged in consecutive order, ascending or descending, is called a scale. But, a chord can be defined as a combination of two or more tones that make up a single block of harmony. Melody is the horizontal aspect of music while harmony, consisting of blocks of tones, or chords, that comprise the vertical aspect of music. Chords have meaning only in relation to the other chords. So, as each chord leads into the next chords the music implies progression and movement in musical space.