In music, an altered chord, an example of alteration, is a chord with one or more diatonic notes replaced by, or altered to, a neighboring pitch in the chromatic scale. For example the following progression uses four unaltered chords:
The next progression uses an altered IV chord and is an alteration of the previous progression:
The A♭ in the altered chord serves as a leading tone to G, which is the root of the next chord.
In jazz and jazz harmony, the term altered chord, notated as an alt chord (e.g. G7alt Play (help·info)), refers to a dominant chord, "in which neither the fifth nor the ninth appears unaltered". – namely, where the 5th and the 9th are raised or lowered by a single semitone, or omitted. Altered chords are thus constructed using the following notes, some of which may be omitted:
- ♭5 and/or ♯5
- ♭9 and/or ♯9
Altered chords may include both a flatted and sharped form of the altered fifth or ninth, e.g. G7♭5♯5♭9; however, it is more common to use only one such alteration per tone, e.g. G7♭5♭9, G7♭5♯9, G7♯5♭9, or G7♯5♯9.
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