The augmented seventh chord , or seventh augmented fifth chord, or seventh sharp five chord is a dominant seventh chord consisting of an augmented triad with a minor seventh. Thus, it consists of a root, major third, augmented fifth, and the minor seventh. Thus in the key of C major it would be C, E, G-sharp, and B-flat as in the figure. It may be notated with the chord symbols C+7, Caug7, or C7♯5, and can be represented by the integer notation {0, 4, 8, 10}.
The root is the only optional note in an augmented seventh chord, the fifth being required because it is raised. This alteration is useful in the major mode because the raised 5th creates a leading tone to the 3rd of the tonic triad.
In rock parlance, the term Augmented seventh chord is sometimes confusingly and erroneously used to refer to the so-called "Hendrix chord", a 7♯9 chord which contains the interval of an augmented ninth but not an augmented fifth.
One chord scale option for a C augmented dominant seventh chord (C E G♯ B♭) is the C whole tone scale: C D E F♯ G♯ A♯/B♭ The augmented minor seventh chord may be considered an altered dominant seventh and may use the whole-tone scale, as may the dominant seventh flat five chord. See chord scale system.
