Harmony (music)

I

Introduction

Harmony (music), the combination of notes (or pitches) that sound simultaneously. The term harmony is used both in the general sense of a succession of simultaneously sounded pitches and for a single instance of pitches sounding together. In this second meaning, the term harmony is synonymous with chord. Harmony stands in contrast to melody (pitches sounding one after another); with melody and rhythm (the stresses and durations of sound), it is one of the three primary elements of music.

Harmony of some sort occurs whenever two or more notes sound at one time in any music: in the interaction of simultaneous melodies in a fugue or in a melody with a descant; in a guitarist's chords accompanying a sung tune; in the blocks of shimmering mouth-organ chords played above the melody in Japanese court music; and in the sustained or insistently repeated pitches (called drones) that provide a background in genres as diverse as Scottish bagpipe music and classical Indian music (See also Polyphony). In Western music, however, especially after the Renaissance, harmony assumed a central role in musical structure and expression.

II

Concepts of Western Harmony

Most Western music of the 17th to the 19th century is tonal—that is, it has a central, or “home,” tone, called the tonic, toward which all other tones seem to gravitate. In tonal music of this period the effect of a tonic is created largely by the interaction of different harmonies with one another. This harmonic language, known as functional harmony, is the subject of much of the following discussion. See also Tonality.

A

Intervals and Triads

Intervals, or pairs of notes, are the building blocks of harmony, and intervals of different sizes have different qualities. Some intervals are consonant (that is, the two notes blend with each other), whereas others are dissonant (that is, the two notes clash, often creating an expectation that they will resolve to a consonance). See also Interval.

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The fundamental harmony in tonal music is a kind of three-note chord called a triad (which means a unity made up of three parts). The three notes of a triad, in Example 1,are called the root, third, and fifth. The third lies above the root by the interval of a third; the fifth lies above the root by the interval of a fifth. See also Chord.

Triads exist in four varieties. Two of these are consonant, that is, they contain only consonant intervals; these two types are the stable chords in tonal music. They are the major triad (for example, C–E–G), in which a major third (C–E) and a perfect fifth (C–G) are formed with the root; and the minor triad (for example, C–Eb–G), in which a minor third (C–Eb) and a perfect fifth are formed with the root. The remaining two types of triad are dissonant. A diminished triad (such as C–Eb–Gb) is formed by a minor third and a dissonant diminished fifth (C–Gb). An augmented triad (such as C–E–G#) is formed by a major third and a dissonant augmented fifth (C–G#).

B

Keys

In functional harmony, in order for a pitch to be a tonic, it must be the focal point of a group of pitches that fall into either of two patterns: the major scale or the minor scale (see Scale). A key consists of a tonic note together with its scale and the triads built on the notes of that scale. Thus, a composition in the key of C major has the note C as its tonic and is structured around the C-major scale.

Triads can be built on any note of a scale, and they are named with Roman numerals according to the scale note that is their root. The triad built on the first note of the scale (the tonic chord or I chord) is the “home” chord. The chord that most often leads to a return of the tonic chord is the triad built on the fifth note of the scale (the dominant chord or V chord). Chords built on the other notes of the scale (the II, III, IV, VI, and VII chords) each have roles to play, both in preparing for the tonic or dominant and in interacting among themselves.

Every triad can be sounded with any of its three notes in the bass, or lowest-sounding part. In root position (with the root in the bass, as in Example 1) the triad is in its most stable form. The inversions of a triad, sounded with other notes of the chord in the bass (such as E–G–C and G–C–E for the root-position triad C–E–G), are more mobile forms of the same harmony.

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