Chords
B Diminished seventh
B · D · F · Ab
The diminished seventh — three stacked minor thirds, dividing the octave into four equal parts.
Also written B°7 · Bo7
B Diminished seventh
B · D · F · Ab
Voicings on the piano
| Voicing | Notes | Play it on your instrument |
|---|---|---|
| Closed, root position | B3 · D4 · F4 · Ab4 | |
| Open (drop 2) | F3 · B3 · D4 · Ab4 | |
| Shell | B3 · D4 · Ab4 | |
| Rootless | B3 · D4 · F4 · G#4 |
Tap a key or a fret to hear it.
Anatomy
B Diminished seventh (Bdim7) contains the notes B · D · F · Ab, each with a role measured as an interval from the root.
Read on: how triads are built · seventh chords
Inversions
An inversion of B Diminished seventh puts a chord tone other than B in the bass; the name after the slash is that bass note.
Where it lives
The keys and the scales B Diminished seventh belongs to.
In which keys
B Diminished seventh is diatonic to 4 keys; the numeral is its degree and the label its harmonic function.
Scales that contain it
B Diminished seventh fits inside these scales, each built on B.
- B Half-Whole DiminishedB · C · D · D# · E# · F# · G# · A
- B UltralocrianB · C · D · Eb · F · G · Ab
- B Locrian 6B · C · D · E · F · G# · A
- B Dorian #4B · C# · D · E# · F# · G# · A
- B Lydian DiminishedB · C# · D · E# · F# · G# · A#
- B DiminishedB · C# · D · E · F · G · G# · A#
- B Composite BluesB · C# · D · D# · E · F · F# · G# · A
- B Messiaen's Mode #7B · C · C# · D · E · E# · F# · G · G# · A#
Understanding the B Diminished seventh chord
Names and symbols
Bdim7 is the chord symbol for B Diminished seventh; it is also written B°7, Bo7.
dim7 and °7 both mean the diminished seventh. A bare dim or ° on a chart sometimes means the triad and sometimes this four-note chord, so the context decides.
How it is built
On B it is B · D · F · Ab, stacking 1P · 3m · 5d · 7d. Every interval in it is a minor third, which makes the chord perfectly symmetrical.
That symmetry means it has only three distinct forms in all twelve keys: invert it and you get another diminished seventh chord, not a different voicing of the same one.
How it is used
Because it belongs to no key it can resolve in four directions with equal plausibility, which made it the standard modulation pivot of nineteenth-century harmony. It is still the fastest way to move somewhere unexpected and make it sound inevitable.
In practice it most often works as a passing chord, sliding chromatically between two diatonic chords.
Learn this properly
Chapter 10: Chords: Triads and SeventhsCommon questions
- What notes are in Bdim7?
- Bdim7 contains B · D · F · Ab. Name any set of notes with the chord identifier.
- Why can a diminished seventh resolve anywhere?
- It divides the octave into four equal minor thirds, so no note is obviously the root. Any of the four can act as a leading tone.
- How many different diminished seventh chords are there?
- Three. Because the chord is symmetrical, all twelve roots produce only three distinct sets of notes.
- What notes are in the B Diminished seventh chord?
- The B Diminished seventh chord contains the notes B · D · F · Ab: the root B with the intervals 1P, 3m, 5d, 7d stacked above it. Play them together for the chord or one after another for an arpeggio. The lowest note is normally B, but any chord tone can take the bass in an inversion.
- What intervals make up the B Diminished seventh chord?
- Measured from B, the B Diminished seventh chord stacks the intervals 1P, 3m, 5d, 7d. The quality of the third and of the seventh, if there is one, is what gives the chord its character; the rest of the notes colour it. Every interval in the formula links to its own page, with its sound.