The augmented seventh chord , or seventh augmented fifth chord,
or seventh sharp five chord is a dominant seventh chord

Dominant seventh chord

In music theory, a dominant seventh chord, or major minor seventh chord,is a chord composed of a root, major third, perfect fifth, and minor seventh. It can be also viewed as a major triad with an additional minor seventh...

 consisting of an augmented triad

Augmented triad

In music, an augmented triad is a triad, or chord, consisting of two major thirds . The term augmented triad arises from an augmented triad being a three note chord, or triad, whose top note is raised, or augmented...

 with a minor seventh

Minor seventh

In classical music from Western culture, a seventh is a musical interval encompassing seven staff positions , and the minor seventh is one of two commonly occurring sevenths. The minor quality specification identifies it as being the smallest of the two: the minor seventh spans ten semitones, the...

. Thus, it consists of a root

Root (chord)

In music theory, the root of a chord is the note or pitch upon which a triadic chord is built. For example, the root of the major triad C-E-G is C....

, major third

Major third

In classical music from Western culture, a third is a musical interval encompassing three staff positions , and the major third is one of two commonly occurring thirds. It is qualified as major because it is the largest of the two: the major third spans four semitones, the minor third three...

, augmented fifth

Augmented fifth

In classical music from Western culture, an augmented fifth is an interval produced by widening a perfect fifth by a chromatic semitone. For instance, the interval from C to G is a perfect fifth, seven semitones wide, and both the intervals from C to G, and from C to G are augmented fifths,...

, 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 C⁷⁵, and can be represented by the integer notation {0, 4, 8, 10}.

The root is the only optional note

Note

In music, the term note has two primary meanings:#A sign used in musical notation to represent the relative duration and pitch of a sound;#A pitched sound itself....

 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

Tonic (music)

In music, the tonic is the first scale degree of the diatonic scale and the tonal center or final resolution tone. The triad formed on the tonic note, the tonic chord, is thus the most significant chord...

. See also dominant

Dominant seventh chord

In music theory, a dominant seventh chord, or major minor seventh chord,is a chord composed of a root, major third, perfect fifth, and minor seventh. It can be also viewed as a major triad with an additional minor seventh...

.

In rock parlance, the term Augmented seventh chord is sometimes confusingly and erroneously used to refer to the so-called "Hendrix chord

Hendrix chord

In music, the dominant 79 chord is sometimes known colloquially as the Hendrix chord or Purple Haze chord, nicknamed for guitarist Jimi Hendrix...

", a 79 chord which contains the interval of an augmented ninth

Ninth

In music, a ninth is a compound interval consisting of an octave plus a second.Like the second, the interval of a ninth is classified as a dissonance in common practice tonality. Since a ninth is a larger than a second, its sonority level is considered less dense.-Major ninth:A major ninth is a...

 but not an augmented fifth.
The augmented minor seventh chord may be considered an altered

Altered chord

In music, an altered chord, an example of alteration, is a chord with one or more diatonic notes replaced by, or altered to, a neighboring pitch in the chromatic scale...

 dominant seventh and may use the whole-tone scale, as may the dominant seventh flat five chord. See chord scale system.

Augmented seventh chord table

Chord	Root	Major third	Augmented fifth	Minor seventh
Caug7	C	E	G	B
	C	E (F)	G (A)	B
	D	F	A	C (B)
Daug7	D	F	A	C
	D	F (G)	A (B)	C
	E	G	B	D
Eaug7	E	G	B (C)	D
Faug7	F	A	C	E
	F	A	C (D)	E
	G	B	D	F (E)
Gaug7	G	B	D	F
	G	B (C)	D (E)	F
	A	C	E	G
Aaug7	A	C	E (F)	G
	A	C (D)	E (F)	G
	B	D	F	A
Baug7	B	D	F (G)	A