Nonchord Tone

A nonchord tone or nonharmonic tone is a note in a piece of music which is not a part of the implied harmony that is described by the other notes sounding at the time. Similarly a chord tone is a note which is a part of the current chord (see: factor (chord)). Nonchord tones are most often discussed in the context of music of the common practice period, but can be used in analysis of other types of tonal music as well.

Chord and nonchord tones are defined by their membership in a chord: "The pitches which make up a chord are called chord-tones: any other pitches are called non-chord-tones." They are also defined by the time at which they sound: "Nonharmonic tones are pitches that sound along with a chord but are not chord pitches."

For example, if a piece of music is currently on a C Major chord, the notes CEG are members of that chord, while any other note played at that time is a nonchord tone. Such tones are most obvious in homophonic music but also often occur in contrapuntal music.

"Most nonharmonic tones are dissonant and create intervals of a second, fourth or seventh", which are required to resolve to a chord tone in conventional ways. If the note fails to resolve until the next change of harmony, it may instead create a seventh chord or extended chord. While it is theoretically possible that for a three-note chord there are (in equal temperament) nine possible nonchord tones, nonchord tones are usually in the prevailing key. Augmented and diminished intervals are also considered dissonant, and all nonharmonic tones are measured from the bass, or lowest note sounding in the chord except in the case of nonharmonic bass tones.

Nonharmonic tones generally occur in a pattern of three pitches, of which the nonharmonic tone is the center: 1 - 2 - 3 Preceding tone - Nonharmonic tone - Following tone (chord tone) - - (chord tone) Preparation - Dissonance - Resolution

Nonchord tones are distinguished through how they are used. The most important distinction is whether they occur on a strong or weak beat and are thus accented or unaccented. They are also distinguished by their direction of approach and departure and the voice or voices in which they occur, and the number of notes they contain.

Over time some nonchord tones supposedly became chord tones, such as the seventh in a seventh chord. In European classical music "The greater use of dissonance from period to period as a result of the dialectic of linear/vertical forces led to gradual normalization of ninth, eleventh, and thirteenth chords; each additional non-chord tone above the foundational triad became frozen into the chordal mass."