Dominant seventh sharp ninth chord

In music, the dominant 7♯9 chord ("dominant seven sharp nine" or "dominant seven sharp ninth") is a chord built by combining a dominant seventh, which includes a major third above the root, with an augmented second, which is the same pitch, albeit given a different note name, as the minor third degree above the root. This chord is used in many forms of contemporary popular music, including jazz, funk, R&B, rock and pop. As a dominant chord in diatonic harmony, it most commonly functions as a turnaround chord, returning to the tonic.

The chord is also sometimes colloquially known, among pop and rock guitarists, as the "Hendrix chord" or "Purple Haze chord", nicknamed for guitarist Jimi Hendrix, who showed a preference for the chord and did a great deal to popularize its use in mainstream rock music. When used by The Beatles it has been called the "Gretty chord" although this can refer to a distinct six-string version.