Altered Chord - Alteration

In music, alteration, an example of chromaticism, is the use of a neighboring pitch in the chromatic scale in place of its diatonic neighbor such as in an altered chord. This should not be confused with borrowing (as in borrowed chord), in which pitches or chords from the parallel key are used in place of those of the original key. Altered notes may be used as leading tones to emphasize their diatonic neighbors. Contrast with chord extension: "Whereas chord extension generally involves adding notes that are logically implied, chord alteration involves changing some of the typical notes. This is usually done on dominant chords, and the four alterations that are commonly used are the ♭5, ♯5, ♭9 and ♯9. Using one (or more) of these notes in a resolving dominant chord greatly increases the bite in the chord and therefore the power of the resolution." "The more tension, the more powerful the resolution...we can pile that tension on to make the resolution really spectacular."

The ♭9 chord is recommended for resolution to minor chords, for example VI7 to ii (G7♭9 to Cm7) in the I-vi-ii-V turnaround. The ♯9 chord is also known as the Purple Haze chord, is most often notated with the enharmonic equivalent ♭3, and is thus used with the blues. The 5 in a ♭5 chord is enharmonically equivalent to a ♯4 or ♯11, but the eleventh chord includes the ♮5 while in the flat chord it is replaced. The ♯5 chord is enharmonically equivalent to a ♭13, does not include the ♮5, and is more common than the ♭13 chord. Both the flat and sharp fifth resolve nicely to the natural ninth.

In jazz, chromatic alteration is either the addition of "notes which are not diatonic to the given scale" or "the expansion of any given progression by adding extra nondiatonic chords". For example, "A C major scale with an added D♯ note, for instance, is a chromatically altered scale" while, "one bar of Cmaj7 moving to Fmaj7 in the next bar can be chromatically altered by adding the ii and V of Fmaj7 on the second two beats of bar" one. Techniques include the ii-V-I turnaround, as well as movement by half-step or minor third.

For example, an altered dominant or V chord may be G♭-B-D♯ (♭5 and ♯9).