Harmony is produced when two or more notes (pitches) sound at the same time. The way those two or more notes sound together produces the harmony. Harmony is the design, progression, and relationship of chords. Chords are a combination of three or more notes blended together. When the pitches agree with each other, we call it consonant, when they disagree, we call it dissonant. Harmony can be as simple as two melodies sounding together, or it can be very complex with many instrumental voices sounding at the same time.
Harmony is an important element of music that a composer may use. Through the use of major, minor and modal harmonies (scale patterns that preceded the major and minor scales), a composer can create a mood or evoke an emotion in the listener.
When a composer chooses to write in a major key, the result often creates a mood that is bright and resolved. Most scales contain eight notes. All scales are made up of a pattern of whole steps (the next note that is one step away) and half steps (this is the smallest distance between two notes). The pattern for the eight notes that make up a major scale is as follows:
When a composer chooses to write in a minor key, the result often creates a mood that is darker or somehow unresolved. The pattern for the eight notes that make up a minor scale is as follows:
Harmonies created in the minor made are less stable than those created in the major mode. This instability results in music which sounds to the listener as if it is somehow in need of resolution, but in an indefinable way. This is very similar to the human emotion of sadness.
We often feel sad, but sometimes it can be hard to tell exactly what makes us sad and how to resolve it. Composers often turn to minor mode when writing music in which they want to convey the emotion of sadness. But it is instability, not sadness, which is characteristic of the minor mode. Music in the minor mode usually portrays stormy conflict much more often than sadness.
The arrangement of the whole steps and half steps are different for the major scale and the minor scale. It is this arrangement that gives the major and minor scales and keys their sounds.