The tense chords
Major and minor triads feel stable. Diminished and augmented chords do not, and that instability is exactly why they are useful: they create tension and movement and then give way to something more stable.
- Diminished: minor third + minor third. A tight, dark, unstable stack. Cdim is C E♭ G♭.
- Augmented: major third + major third. A wide, symmetrical, restless stack. Caug is C E G♯.
| Chord | Formula | Notes on C | Sounds |
|---|---|---|---|
| Cmajor | 1 3 5 | C E G | bright and settled |
| Cmminor | 1 ♭3 5 | C E♭ G | darker and more serious |
| C°diminished | 1 ♭3 ♭5 | C E♭ G♭ | tense, unstable, a little spooky |
| C+augmented | 1 3 ♯5 | C E G♯ | dreamy and restless, with no clear home |
| C°7diminished 7th | 1 ♭3 ♭5 𝄫7 | C E♭ G♭ B𝄫 | dramatic and very unstable |
| Cø7half-diminished | 1 ♭3 ♭5 ♭7 | C E♭ G♭ B♭ | dark and bittersweet |
| C7♯5augmented 7th | 1 3 ♯5 ♭7 | C E G♯ B♭ | tense with a wobble |
Diminished chords
A diminished triad is a minor chord with the fifth lowered by a half step. It has two minor thirds stacked, so the root and the fifth are a tritone (six half steps) apart, the most unstable interval in music. That is where its tension comes from.
Three ways to use a diminished chord
- As a passing chord. Place it a half step below the chord you are heading to. In C, C → C♯dim → Dm glides up smoothly: the diminished chord has no home of its own and pulls into the next chord.
- As vii° in a major key. The B° chord in C major shares most of its notes with G7, and works as a stand-in for it. It resolves to C.
- As ii° in a minor key. In A minor, B° leads to E (the V) and then to Am. With a minor seventh added (Bø7) it is the classic jazz ii-V-i.
Diminished 7th and half-diminished
Add a seventh to a diminished triad and you get two very different chords. Half-diminished (m7♭5, ø7) adds a minor seventh, which softens it: it is the usual ii chord in a minor key. Fully diminished 7th (°7) adds a diminished seventh, which gives four equal minor thirds. It is as symmetrical as a chord can be, so C°7, E♭°7, G♭°7 and A°7 are all the same four notes. That makes it a favourite for changing key: any of its notes can be treated as the root.
Augmented chords
An augmented triad is a major chord with the fifth raised a half step. Two major thirds stack to exactly an octave when you add a third one, so the chord is perfectly symmetrical: C+, E+ and A♭+ are the same notes. With no strong centre, it floats.
Using augmented chords
- On the V chord: G+ (G B D♯) leads naturally up to the C, because D♯ rises to E. The raised fifth is a leading note.
- As a lift: a major chord to its augmented version and on to the 6th (C → C+ → C6) is a stepwise climb used in pop, jazz and soul.
- Sparingly. One augmented chord goes a long way. It sounds dreamy, eerie, or comic, depending on the tempo.
How to practise
- Warm-up: tell major, diminished and augmented apart on white-key roots, with note names on the keys. Look for the two stacked minor thirds or two stacked major thirds.
- Working set: every root, with minor chords mixed in. You build chords too.
- Heavy lift: diminished 7th, half-diminished and augmented 7th, in inversions. Remember that dim7 chords have four names, so the drill gives you the root.
Get the foundations with the interval builder (these chords are just stacked thirds), try the suspended chords and seventh chords next, or see the whole picture in the chord types guide. Guitar and ukulele shapes are in the chord library.
Frequently asked questions
What is a diminished chord?
A diminished triad stacks two minor thirds: root, minor third and diminished fifth (C E♭ G♭). It is tense and unstable and wants to move to another chord.
What is an augmented chord?
An augmented triad stacks two major thirds: root, major third and augmented fifth (C E G♯). It sounds restless and dreamy, with no clear home, because it is perfectly symmetrical.
What is the difference between diminished 7 and half-diminished?
Both are built on a diminished triad. Fully diminished 7 (C E♭ G♭ B𝄫, which sounds like C E♭ G♭ A) stacks minor thirds all the way. Half-diminished (m7♭5: C E♭ G♭ B♭) has a minor seventh instead, which is less tense.
Why does a diminished 7th chord have four possible names?
It is built from equal minor thirds, so it divides the octave into four equal parts. C°7, E♭°7, G♭°7 and A°7 are the same four notes. Any of them can be the root, which makes it a favourite for changing key.
How do I use a diminished chord?
As a passing chord between two others: C to C♯° to Dm is a classic, with the diminished chord a half step below its target. The vii° chord in a major key also works as a substitute for V7.
How do I use an augmented chord?
Usually briefly, on the V chord, where the raised fifth leads up to the tonic note of the next chord (G+ to C). It can also move up by half steps for a dreamy lift, such as C to C+ to C6 to C7, as in many jazz and pop tunes.
What does ø mean in a chord symbol?
The ø symbol means half-diminished (m7♭5). A small circle ° means diminished. So Bø7 is B D F A, and B°7 is B D F A♭.
Where does a diminished chord occur naturally in a key?
On the 7th degree of a major scale (B° in C major) and on the 2nd degree of a minor scale (B° in A minor). That is the only diminished triad in the key.