In these genres, chords often include added ninths, elevenths and thirteenths and altered variants, such as flat ninths, sharp ninths, sharp elevenths and flat thirteenths. Jazz from the 1930s onward, jazz fusion from the 1970s and onward and funk all use extended chords as a key part of their sound.
The eleventh chord is an exception to this voicing, in which the root, seventh, ninth, and eleventh are most commonly used. For example: in a thirteenth chord, one would play the root, third, seventh, and thirteenth, and be able to leave out the fifth, ninth, and eleventh without affecting the function of the chord. Any notes which happen to be altered, such as a flatted fifth or ninth, should also be given priority.
The seventh factor helps to define the chord as an extended chord (and not an added note chord), and also adds to the texture. The extended note defines the quality of the extended pitch, which may be major, minor, perfect, or augmented. The third defines the chord's quality as major or minor. The root is never omitted from the texture. Generally, priority was given to the third, seventh and the most extended tone, as these factors most strongly influence the quality and function of the chord. During the common practice period of Western classical music, composers orchestrating chords that are voiced in four or fewer parts would select which notes to use so as to give the desired sonority, or effect of the intended chord.
