So What chord
In jazz and jazz harmony, a So What chord is a particular 5-note chord voicing. From the bottom note upwards, it consists of three perfect fourth intervals followed by a major third interval. It was employed by Bill Evans in the "'amen' response figure" to the head of the Miles Davis tune "So What".
For example, an "E minor" So What chord (see illustration) is an Em7sus4 voicing, or as a polychord:
The So What chord is often used as an alternative to quartal voicings and may be used in diatonic and chromatic planing, and is identical to the standard tuning of a guitar's five lowest strings. It is essentially a minor eleventh chord (-11, m11), arranged as it would be played on a guitar (root, 4th, ♭7th, ♭3rd, 5th).
It may also be thought of as a five-note quartal chord (built from fourths) with the top note lowered by a semitone. More modern sounding than "tertial chords" (built from thirds), it is useful in comping; since the structure of quartal harmony is usually vague, many roots may be applied to the So What chord and it may work well in various contexts including, "a major scale context; a Mixolydian mode context; or a minor context". For example, the E chord described above can also be C6Δ9, Asus479, G69, Dsus246 [no 7], Flydian (FΔ9♯1113 [no 5]) or F♯phrygian (F♯m7♭911♭13 [no 5]).
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