
Altered chords are chords that are modified or "altered" from their basic major or minor triad or seventh chord structure by changing one or more of their notes.
The alterations usually involve raising or lowering the fifth, ninth, or eleventh notes of the chord, and are used to create a more dissonant, tense, or colorful sound.
In jazz and other styles of modern music, altered chords are often used to create tension and harmonic interest.
For example, a dominant 7th chord with a flattened 9th (often written as "7b9") can be used to create a bluesy or jazzy sound.
Similarly, a dominant 7th chord with a raised 5th (often written as "7#5") can be used to create a more exotic or tense sound.
Some examples of altered chords include:
- Dominant 7th chords with a flattened 9th (7b9)
- Dominant 7th chords with a raised 9th (7#9)
- Dominant 7th chords with a flattened 5th (7b5)
- Dominant 7th chords with a raised 5th (7#5)
- Minor 7th chords with a flattened 5th (m7b5 or half-diminished)
- Major 7th chords with a flattened 5th (M7b5 or diminished-major)
Altered chords can add a lot of harmonic interest to a chord progression, but they should be used judiciously and with a clear understanding of their harmonic function.