Chords
Diminished chord
A diminished chord is a triad made of two stacked minor thirds: a root, a minor third and a diminished fifth, such as B D F for Bdim.
What is a diminished chord?
A diminished chord is the triad with the formula 1 ♭3 ♭5: two minor thirds stacked (3 + 3 semitones). The distance from root to fifth is therefore 6 semitones, a tritone, the most unstable interval in the scale. That interval is where the chord's tension comes from.
Spellings: Bdim = B D F, C♯dim = C♯ E G, F♯dim = F♯ A C, G♯dim = G♯ B D. Symbols: "dim" or "°" (B°).
Where does the diminished chord appear in a key?
In a major key, the diminished chord sits on the 7th degree (vii°): Bdim in C, F♯dim in G, C♯dim in D. In natural minor, it sits on the 2nd degree (ii°): Bdim in A minor.
Bdim contains B and F, the two notes that create the tension in G7. So Bdim behaves like a G7 without its root: it wants to resolve to C, with B rising to C and F falling to E.
How do you play a diminished chord on guitar?
On strings 3, 2, 1 (G, B, high E), play Bdim at frets 4, 3, 1 (B D F). The shape is movable: up one fret for Cdim (C E♭ G♭), up two for C♯dim.
A four-string shape with the root on the 5th string: Bdim = x2343x (B F B D). Slide it to the 4th fret for C♯dim = x4565x (C♯ G C♯ E). Mute the 6th and 1st strings with your spare fingers. To double-check any shape, enter its notes in the chord identifier.
Exercise: the diminished passing chord
The most common use on guitar is to connect two chords a whole step apart:
- C
x32010 - C♯dim
x4565x - Dm
xx0231 - G7
320001
The bass climbs C, C♯, D: the C♯dim adds one beat of tension that resolves naturally into Dm. Give C♯dim two beats, then try the same move between F xx3211 and G 320003, using F♯dim xx421x (F♯ A C).
Common mistakes with diminished chords
- Mixing up "°" and "ø": B° is diminished, Bø is half-diminished (Bm7♭5 = B D F A).
- Assuming dim always means dim7: on jazz charts C° often means a diminished seventh (C E♭ G♭ A). In pop or classical writing, Cdim is a triad. Context decides.
- Letting it sit: a diminished chord is built to move. Held for four bars, it just sounds wrong.
Key takeaways
- Formula: 1 ♭3 ♭5, two minor thirds, a tritone between the outer notes.
- It is vii° in major keys and ii° in minor keys.
- Basic top-string shape: frets 4, 3, 1 for Bdim.
- Key use: chromatic passing chord (C, C♯dim, Dm).
Frequently asked questions
Why does a diminished chord sound so tense?
It contains a tritone (B-F in Bdim), which splits the octave into two equal halves and has no stable footing. Your ear expects a resolution, usually a semitone up: Bdim to C, C♯dim to Dm.
What is the difference between Cdim and Cdim7?
Cdim is a triad: C E♭ G♭. Cdim7 adds a diminished seventh (B♭♭, which sounds as A): C E♭ G♭ A. The dim7 is symmetrical, built entirely from minor thirds.
What scale do you play over a diminished chord?
Over a vii° (Bdim in C), the notes of the key work fine: the C major scale. Over a passing diminished or a dim7, the whole-half diminished scale fits every chord tone.
Related terms
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