Neighboring tone

A nonchord tone (NCT), nonharmonic tone, or embellishing tone is a note (i.e., a pitch) in a piece of music or song that is not part of the implied or expressed chord set out by the harmonic framework. Similarly, a chord tone is a note that is a part of the functional chord (see: factor (chord)). Nonchord tones are most often discussed in the context of the common practice period of classical music, but they can be used in the analysis of other types of tonal music as well, such as Western popular music.

Chord and nonchord tones are defined by their membership (or lack of 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 an excerpt from a piece of music implies or uses a C major chord, then notes C, E and G are members of that chord, while any other note played at that time (e.g., notes such as F♯) is a nonchord tone. Such tones are most obvious in homophonic music but occur at least as frequently 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.

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