What Is an Augmented 7th Chord?
An augmented 7th chord is an augmented triad with a minor 7th added above the root. It's essentially a dominant 7th chord with a raised (augmented) 5th — giving it a more colourful, chromatic quality.
In jazz theory, this chord is written as C7#5 or C7+ and belongs to the family of altered dominant chords — dominant 7th chords with chromatically modified notes for extra tension and colour.
How to Build an Augmented 7th Chord
Formula
Root + Major 3rd + Augmented 5th + Minor 7th
Semitones: 0 — 4 — 8 — 10
Example: C Augmented 7th
- C (root)
- E (4 semitones = major third)
- G# (8 semitones = augmented fifth)
- B♭ (10 semitones = minor seventh)
vs. Dominant 7th: C7 = C E G B♭. C7#5 = C E G# B♭. The only difference is the raised 5th — but it changes the chord's sound significantly.
All 12 Augmented 7th Chords
| Chord | Root | Major 3rd | Aug. 5th | Minor 7th |
|---|---|---|---|---|
| C7#5 | C | E | G# | B♭ |
| G7#5 | G | B | D# | F |
| D7#5 | D | F# | A# | C |
| A7#5 | A | C# | E# | G |
| E7#5 | E | G# | B# | D |
| B7#5 | B | D# | Fx | A |
| F#7#5 | F# | A# | Cx | E |
| F7#5 | F | A | C# | E♭ |
| B♭7#5 | B♭ | D | F# | A♭ |
| E♭7#5 | E♭ | G | B | D♭ |
| A♭7#5 | A♭ | C | E | G♭ |
| D♭7#5 | D♭ | F | A | C♭ |
The Sound of an Augmented 7th Chord
Tense, colourful, chromatic, driving, slightly eerie.
The augmented 7th has all the tension of a dominant 7th chord but with a more colourful, chromatic edge from the raised 5th. It sounds like a dominant 7th that has been "supercharged" — more unstable, more directional, and more interesting.
Jazz pianists like Bill Evans and Herbie Hancock use altered dominants (including 7#5) to add colour to standard ii-V-I progressions without fundamentally changing the harmony.
How to Use Augmented 7th Chords
1. As an altered V7: Substitute C7#5 for C7 in a V7-I progression for extra colour. The resolution still works, just with more chromatic tension.
2. In jazz chord substitution: Use augmented dominant 7ths to add chromatic interest to standard progressions.
3. In blues: The 7#5 sound is common in more advanced blues playing, giving a jazzier edge to the basic blues framework.
4. In film scoring: Augmented dominant chords create a sense of unease and forward momentum.
Free: Chord Ear Training Cheat Sheet
Train your ear to hear the difference between plain dominant 7th and augmented 7th chords.