Chord extensions

Chord extensions are essentially chord tones that are added above the basic 7^th chord structure (R-3^rd-5^th-7^th). The possible extensions are the 9^th, 11^th, and 13^th. These extensions don't replace the R-3^rd-5^th-7^th but are added in addition to achieve a desired sound.

1. What are extended chords used for?
2. Why does jazz use extended chords?

What are extended chords used for?

Extended chords are generally used when a richer harmonic “color” is desired. Since 9th chords are among the most popular extended chords, let's begin with them. If you were to take a Cmaj7 chord (C-E-G-B) and add a D note to the voicing, you would be creating a Cmaj9 (R[oot]-3–5-7-9; C-E-G-B-D).

Why does jazz use extended chords?

By using extended chords, you can keep common tones between chords for smoother voice leading. For example, “G” is the highest note in bar 7 and the first beat of bar 8. So, three different voicings have the same melody note on top. This technique is often used in turnarounds as shown in this example.