EXTENSIONS / POLYCHORDS

Chord extensions refer to adding to, or extending, a triad. This includes 7ths, 9ths, 11ths, 13ths and their alterations. Knowing how to voice extended chords is crucial to jazz ensemble writing. Here are a few general rules to follow:

1. Use major seventh intervals, or its inversion, minor seconds. Sharp nines (#9) should be voiced above major thirds and thirteenths (13) above sevenths (7).
2. Avoid minor ninths. This is created when not following the above rule.
3. Do not write the extended notes too low, generally above F below middle C.
4. Sometimes thinking of extended chords as polychords is helpful. See North Rim examples below.

Abene's voicings below are very dense. The first, third, and seventh bars use six-part density; the fifth bar is seven-part density. Notice the use of the M7th intervals.

Sometimes chords can not be easily understood using traditional chord symbol notation. In this case polychord symbols should be used. Polychords are written using a horizontal line to separate the two chords, indicating both chords are to be played together. This is different from inverted chords which use a diagonal line to indicate a bass note other than the root.