Thirteenth

In music or music theory, a thirteenth is the note thirteen scale degrees from the root of a chord and also the interval between the root and the thirteenth. The thirteenth is most commonly major Play^ⓘ or minor Play^ⓘ.

A thirteenth chord is the stacking of six (major or minor) thirds, the last being above the 11th of an eleventh chord.^[1] Thus a thirteenth chord is a tertian (built from thirds) chord containing the interval of a thirteenth, and is an extended chord if it includes the ninth and/or the eleventh. "The jazzy thirteenth is a very versatile chord and is used in many genres."^[2] Since 13th chords tend to become unclear or confused with other chords when inverted, they are generally found in root position.^[3] For example, depending on voicing, a major triad with an added major sixth is usually called a sixth chord Play^ⓘ, because the sixth serves as a substitution for the major seventh, thus considered a chord tone in such context.

However, Walter Piston, writing in 1952, considered that, "a true thirteenth chord, arrived at by superposition of thirds, is a rare phenomenon even in 20th-century music."^[4] This may be due to four-part writing, instrument limitations, and voice leading and stylistic considerations. For example, "to make the chord more playable [on guitar], thirteenth chords often omit the fifth and the ninth."^[5]