Extended Chords

Triad extensions begin with adding the 7^th above the root.  Like climbing a ladder built on thirds, the 9^th, 11^th, and 13^th are the upper extensions that may be added to any chord.  The scale degree represented by these extensions can be calculated by subtracting the number 7 from each extension.  A 9^th is the same note as a 2^nd, the 11^th same as a 4^th, and the 13^th same as a 6^th.

Theorists do not generally call notes added to the triad extensions unless the 7^th is present.  If it is not present, they refer these vertical structures as added-note chords.  The “add 2” chord is not referred to as a 9^th chord without the 7^th contained in the chord.  Similarly an “add 6" chord is not referred to as a 13^th chord.  Chords with extensions above the 7^th are sometimes referred to as tall chords.

Extended triads became popular in the music of the Impressionists in the late 18^th and early 20^th centuries.  Among the composers in this style were Debussy, Ravel, and Faure.  Extended triads are a hallmark of Jazz harmony, and upper extensions are added to most chords by arrangers, keyboardists, and guitarists.  This practice gives Jazz its unique harmonic flavor.  Look at the Lead Sheet Symbols guide in the Materials below.  At a keyboard, slowly roll the extended chords from the bottom up to learn how to distinguish them aurally.  Then try creating harmonies with extended chords beginning with just the 3^rd and 7^th above the bass note, and add the 9^th and 13^th within the octave.  These extensions replace the root and 5^th in the upper structure.