Augmented chord: what it is and how to build it
An augmented chord is a triad made of two stacked major thirds: root, major third and augmented fifth, 4 + 4 half steps. It sounds dreamy and unsettled, and it divides the octave into three equal parts.
An augmented chord is a three-note chord made by stacking two major thirds. It is the widest of the four basic triads. It sounds floating and unresolved, as if the music has lifted off the ground. Composers use it for dreamlike moments, for building tension, and for gliding from one chord to the next.
On this page you will learn how to build an augmented chord on any note, how to write its symbol, why it is so symmetrical and how it can lead to other chords.
How do you build an augmented chord?
Start from the root. Count 4 half steps to the third. Count 4 more to the fifth. The formula is 4 + 4. If you already know a major chord (4 + 3), simply raise the fifth by one half step. The root-to-fifth distance becomes 8 half steps, which is an augmented fifth.
| Step | Interval from the root | Half steps from the root |
|---|---|---|
| Root | unison | 0 |
| Third | major third | 4 |
| Fifth | augmented fifth | 8 |
How do you write an augmented chord symbol?
The usual symbols are the root followed by aug (Caug) or a plus sign (C+). In Roman numeral analysis an augmented chord is written with a plus sign after an uppercase numeral, for example III+. You may also see C7♯5 for an augmented chord with a dominant seventh added.
Why is the augmented chord symmetrical?
Every interval in an augmented triad is 4 half steps, and three of them add up to 12, a full octave. That means the chord divides the octave into three equal parts. If you invert it, you get exactly the same set of intervals again.
A surprising result is that one augmented chord contains the notes of two others. The notes C, E and G♯ sound the same as E, G♯ and C, and as G♯, C and E. So there are only four different augmented triads in all, even though there are twelve possible roots. Each triad can be named from any of its three notes.
| Chord | Notes | Same sounds as |
|---|---|---|
| C augmented | C, E, G♯ | E aug and A♭ aug |
| D♭ augmented | D♭, F, A | F aug and A aug |
| D augmented | D, F♯, A♯ | F♯ aug and B♭ aug |
| E♭ augmented | E♭, G, B | G aug and B aug |
The spelling you choose depends on the key you are in. In a key with sharps you would write C, E, G♯. In a key with flats the same sounds might be spelled A♭, C, E. Either way, the chord is the same set of keys on the piano.
Where does an augmented chord appear in a key?
An augmented triad does not occur naturally in a major scale. It appears on the third note of the harmonic minor scale. In A minor, the chord built on C is C, E and G♯, which is C augmented. The G♯ is the raised seventh note of A harmonic minor. See harmonic minor scale.
Composers also use it as a passing chord. In C major, play C major, then C augmented (the G rises to G♯), then F major. The rising line G, G♯, A gives a smooth, stepwise motion.
How does an augmented chord sound?
Augmented chords sound dreamy, magical, ambiguous or suspenseful. There is no sense of home, because the chord does not have the stable perfect fifth that major and minor chords have. Film and television music uses them for moments of wonder or surprise, and jazz players use them over the V chord to add color.
What is the difference between augmented and diminished chords?
They are opposites. A diminished triad has two minor thirds (3 + 3) and is the narrowest. An augmented triad has two major thirds (4 + 4) and is the widest. Both are unstable, but a diminished chord feels compressed while an augmented one feels stretched. Read the page on the diminished chord to compare them.
How can you practice augmented chords?
- Play a C major chord with fingers 1, 3 and 5.
- Raise the top note by one half step, from G to G♯, with your little finger.
- Listen to the changed sound, then play it again ending on F major.
- Move the same shape up four half steps and notice that you play the same keys in a different order.
Memory trick: augmented means bigger. Take a major chord and make the fifth one half step bigger, from 7 half steps to 8.
Check yourself
1. What is the half step formula for an augmented triad?
Answer: 4 + 4. Two major thirds stacked, 4 half steps each, make an augmented triad.
2. How do you turn a major chord into an augmented chord?
Answer: Raise the fifth. Raising the fifth by one half step turns 4 + 3 into 4 + 4.
3. How many different augmented triads (by sound) are there?
Answer: 4. Each augmented triad splits the octave evenly, so every one repeats on three different roots.
4. Which symbol means augmented?
Answer: C+. A plus sign or aug marks an augmented chord.
5. Which scale gives a natural augmented chord on its third note?
Answer: Harmonic minor. The raised seventh of harmonic minor creates III+.