Bbdim7 guitar chord
The third voice from the top lowered an octave. The dropped voice becomes the bass, which is why a string is skipped.
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About Bbdim7 — drop 3 voicings
Bbdim7 is Bb, Db, Fb and G — Bbdim with a diminished seventh stacked on top.
It sounds suspenseful and rootless. Three stacked minor thirds divide the octave evenly, so the same four notes spell four dim7 chords and the shape repeats every three frets.
Bbdim7 notes and formula
| Bb | Db | Fb | G |
|---|---|---|---|
| 1 | ♭3 | ♭5 | ♭♭7 |
Leading-tone or passing chord — it can resolve almost anywhere.
Also written Bb°7, Bbo7 or Bb diminished 7. The same chord either way; which spelling you meet depends on who wrote the chart.
How to play Bbdim7
The same operation one voice further down: the third voice from the top falls an octave and becomes the bass.
That leaves a bigger hole under the top three notes, so a string gets skipped: the muted string in the middle is the shape, not a mistake.
Bbdim7 has 10 of them, on strings 5-3-2-1 and strings 6-4-3-2, from open position up to the 14th — every inversion the chord has: Bb in the bass, Db in the bass, Fb in the bass and Abb in the bass. The one to learn first is the Bb shape at the nut.
5 of them sit on strings 5-3-2-1, so you can run the inversions up one set without changing strings — which is the whole reason to learn them as a family rather than as separate grips.
Start with x12020 — no barre and 2 open strings. 1 of the 8 shapes here sits in open position. 2 of the 8 need a barre. Together they cover the neck from the 1st fret to the 15th.
| Frets | Where | Bass | Top | Hand |
|---|---|---|---|---|
| x12020 | open position | Bb, root position | Fb | 2 open strings |
| xx2323 | 2nd fret | Fb, 2nd inversion | G | all fretted |
| 6x5656 | 5th fret | Bb, root position | Bb | barred |
| 678686 | 6th fret | Bb, root position | Bb | barred |
| xx8989 | 8th fret | Bb, root position | Db | all fretted |
| x-x-11-12-11-12 | 11th fret | Db, 1st inversion | Fb | all fretted |
| x-13-14-12-14-12 | 12th fret | Bb, root position | Fb | all fretted |
| x-x-14-15-14-15 | 14th fret | Fb, 2nd inversion | G | all fretted |
The same notes rebuilt from scratch give 6 shell, 14 drop 2 and 6 open string voicings, each on its own page.
Tensions. A shell of Bbdim7, root, third and seventh, leaves a string free, and the tones that belong over it are the 9 (C), the 11 (Eb), the b13 (Gb) and the maj7 (A).
How to use Bbdim7
A diminished seventh divides the octave evenly, so Bbdim7 has no single root and no single destination: it can lead to Eb or to B, and it is the same four notes either way.
What to play over Bbdim7
Every note of Bbdim7 is in Bb diminished and Bb half-whole diminished.
Chords near Bbdim7
Change one note of Bbdim7 and you have Bbdim (drop the sixth), Bbm6 (the flat fifth becomes a fifth), Bbm7b5 (the sixth becomes a flat seventh) or BbmMaj7b5 (the sixth becomes a major seventh).
Bbdim7 is a diminished chord — root, minor third, flat fifth. Diminished and half-diminished chords on every root.
On Bbdim7’s sound and use this page follows Stefan Kostka, Dorothy Payne & Byron Almén, Tonal Harmony (McGraw-Hill, 8th ed., 2018). The shapes and the derived voicings come from different places, and both are explained in where the chords and the theory come from.