HearmonyAugmented Chord: What It Is, How to Build It and How It Sounds
An augmented chord is a three-note chord made of two major thirds stacked on top of each other. C augmented (written Caug or C+) is C, E, G♯: a C major chord with its top note raised a half step. It sounds bright but stretched and dreamy, as if it is floating and waiting to land somewhere.
Below you will find the spelling in every key, why there are really only four different augmented chords, where the chord shows up in music and how to hear it next to major and diminished.
What is an augmented chord?
An augmented chord, or augmented triad, has a root, a major third (4 semitones up) and an augmented fifth (8 semitones up). Counted note to note, that is 4 semitones and then 4 more. Its name comes from that fifth: a perfect fifth made one half step larger, or "augmented".
On chord charts it appears as Caug, C+ or C(♯5). In Roman numerals it gets an uppercase numeral with a plus sign, such as V+ or III+. The Wikipedia article on the augmented triad lists the less common notations.
It is one of the four basic triad types, next to major, minor and diminished. How all four are built from thirds, and which ones appear in a key, is covered in the guide to triads.
How do you build an augmented chord?
The quickest way to build an augmented chord is to take a major chord and raise its fifth by a half step. C major (C E G) becomes C augmented (C E G♯). You can also stack two major thirds: C up to E, then E up to G♯.
Spell the top note as a sharpened fifth, not a flattened sixth. C augmented is C E G♯, not C E A♭, even though G♯ and A♭ are the same key on a piano. A triad always uses every other letter (C, E, G), so the fifth must be some kind of G.
| Chord | Notes | Chord | Notes |
|---|---|---|---|
| Caug | C E G♯ | G♭aug | G♭ B♭ D |
| D♭aug | D♭ F A | Gaug | G B D♯ |
| Daug | D F♯ A♯ | A♭aug | A♭ C E |
| E♭aug | E♭ G B | Aaug | A C♯ E♯ |
| Eaug | E G♯ B♯ | B♭aug | B♭ D F♯ |
| Faug | F A C♯ | Baug | B D♯ F𝄪 |
Some spellings look odd because of the letter rule: E augmented ends on B♯ (played as C), A augmented on E♯ (played as F) and B augmented on F𝄪, F double sharp (played as G).
Why are there only four augmented chords?
There are only four different-sounding augmented chords because the chord splits the octave into three equal major thirds. From C, up a major third is E, up another is G♯, and one more major third brings you back to C an octave higher. Every note in the chord sits the same distance from the next.
That means C augmented, E augmented and G♯ (or A♭) augmented contain the same three keys on the piano. Only the name and the spelling change, depending on which note the music treats as the root. All twelve augmented chords fall into four groups:
| Group | Keys on the piano | Names that share them |
|---|---|---|
| 1 | C, E, G♯/A♭ | Caug, Eaug, A♭aug |
| 2 | C♯/D♭, F, A | D♭aug, Faug, Aaug |
| 3 | D, F♯, A♯/B♭ | Daug, F♯aug, B♭aug |
| 4 | E♭, G, B | E♭aug, Gaug, Baug |
The symmetry has a consequence for your ear: an augmented chord in first or second inversion still sounds like a root-position augmented chord, just on a different root. E G♯ C is C augmented in first inversion, but it sounds exactly like E augmented (E G♯ B♯). The diminished 7th chord has the same trick with minor thirds, which is why there are only three of those.
What does an augmented chord sound like?
An augmented chord sounds bright, wide and unresolved. It keeps the major third of a major chord, so it is not dark, but its raised fifth has no stable partner, so the ear hears it as a chord in motion rather than a place to stop. Descriptions you will often meet are dreamy, suspenseful, eerie and "like a question".
The raised fifth also tends to keep rising. In C augmented, the G♯ leans up a half step toward A, which is where most uses of the chord come from.
Where is the augmented chord used?
The augmented chord is used mostly as a passing color between two stable chords, and much less often than major, minor or the dominant 7th. Three uses cover most of what you will hear:
- V+ to I. In C major, raise the fifth of the G chord: G B D♯. The D♯ pushes up to E, the third of C, so the pull home gets stronger. The same chord often appears with a seventh added (G7♯5 or G+7).
- A rising inner line. Hold a major chord and move its fifth up by half steps: C, C+, C6, C7 (the top line goes G, G♯, A, B♭). This line cliché is common in standards, show tunes and older pop.
- III+ in minor. In A minor with the raised seventh G♯ (harmonic minor), the chord on the third degree is C E G♯, an augmented triad that grows naturally inside the key.
A well-known rock example is the Beatles' "Oh! Darling", whose intro is a single E augmented chord before the song lands on A, the home chord. Augmented chords also belong to the whole-tone scale (C D E F♯ G♯ A♯ contains both C augmented and D augmented), the floating scale associated with Debussy and with dream sequences in film music.
One naming trap: an "augmented sixth chord" in classical theory is a different chord, built around an augmented sixth interval (A♭ to F♯ in C major), and has nothing to do with the augmented triad.
Augmented vs diminished: what's the difference?
An augmented chord stacks two major thirds (4 + 4 semitones), while a diminished chord stacks two minor thirds (3 + 3). Both are unstable and both have an altered fifth, but augmented sounds stretched outward and diminished sounds squeezed inward.
| Chord | Notes in C | Semitone stack | Fifth | Sound |
|---|---|---|---|---|
| Major | C E G | 4 + 3 | perfect | bright, stable |
| Augmented | C E G♯ | 4 + 4 | augmented | bright, stretched, floating |
| Minor | C E♭ G | 3 + 4 | perfect | dark, stable |
| Diminished | C E♭ G♭ | 3 + 3 | diminished | dark, tense, squeezed |
The full story of the squeezed chord, including the half-diminished and diminished 7th, is in the guide to the diminished chord.
How to recognize an augmented chord by ear
To recognize an augmented chord by ear, first decide whether the chord could end a song. If it is bright but cannot rest, it is very likely augmented.
- Play C major, then C augmented. Only the top note moves, up a half step. Notice the chord lift off the ground.
- Play C augmented, then C diminished. Both are restless: compare bright and stretched with dark and squeezed.
- Play G+ then C. Feel the D♯ slide up into E.
- Arpeggiate the chord from low to high. Two equal large steps (4 + 4) are the fingerprint of augmented.
Common mistakes and how to fix them
- Hearing it as major. The bright third dominates in a quick passage. Fix: listen only to the top note and ask whether it wants to rise.
- Mixing it up with diminished. Both feel unresolved. Fix: bright means augmented, dark means diminished.
- Naming the wrong root. Because of the symmetry, C+, E+ and A♭+ sound alike. Fix: take the root from the bass note and the key, not from the sound of the chord alone.
Self-test: which of these are augmented? E♭ G B · D F♯ A · F A C♯ · G B D♯ · A C E. Answers: E♭ G B, F A C♯ and G B D♯ are augmented; D F♯ A is major and A C E is minor.
Practice augmented chords in Hearmony
Hearmony's Chord Garden adventure has a unit called Dreamy chords that plays C augmented next to C major ("two major thirds stacked, dreamy and unresolved") and then mixes it with major, minor and diminished in short quizzes and matching questions. In the early lessons each chord is played note by note before it sounds together, so you can hear the two equal steps. The Garden mix that follows adds sus chords and an odd-one-out drill across all four triad types, and the Seventh Heaven adventure brings augmented chords back in inversions.
Chord Garden is part of Hearmony Pro, while the first adventure and the theory side quests are free. For every chord type side by side, see types of chords and how each one sounds, and for where chord quality fits in a daily routine, start with ear training exercises for beginners.