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A chord extension is a note added to a basic triad to create a richer and more colorful sound. The most common chord extensions are the 7th, 9th, 11th and 13th.
What is a chord extension?
Chord extensions are created by stacking additional thirds on top of a basic chord. While a major or minor triad contains three notes, extended chords add one or more extra notes to create greater harmonic richness.
For example, a Cmaj7 chord adds a major seventh to a C major triad, while a C9 chord extends the harmony even further. In practical piano playing, some notes—such as the fifth—are often omitted to make extended chords easier to play and to avoid a muddy sound.
How are chord extensions used in piano playing?
Chord extensions are one of the easiest ways to make piano accompaniment sound more professional and expressive. Adding a seventh, ninth or other extension can transform a simple chord into a richer and more modern harmony.
Learning how to voice chord extensions clearly is an important piano skill. Good voicings allow the added notes to enhance the harmony without making the chord sound crowded, especially in the lower register.