Gdim7 guitar chord
Root, third and seventh: the guide tones fix the quality, so the fifth is dropped. That is what leaves a string free, so pick a tension to put on top.
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About Gdim7 — shell voicings
Gdim7 is G, Bb, Db and Fb — Gdim 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.
Gdim7 notes and formula
| G | Bb | Db | Fb |
|---|---|---|---|
| 1 | ♭3 | ♭5 | ♭♭7 |
Leading-tone or passing chord — it can resolve almost anywhere.
Also written G°7, Go7 or G diminished 7. The same chord either way; which spelling you meet depends on who wrote the chart.
How to play Gdim7
Root, third and seventh. The third and seventh, the guide tones, are what make the chord major, minor or dominant, so the fifth can go: it says nothing the symbol needs.
Three notes means a spare string, which is the real point. Put a tension on it.
Gdim7 has 6 of them, on strings 6-4-3-2, strings 5-3-2-1, the bottom four strings and the middle four strings, from open position up to the 14th — all in one inversion, so the bass note never moves. The one to learn first is the G shape at the nut.
Start with 31x320 — no barre and 1 open string. 2 of the 8 shapes here sit 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 |
|---|---|---|---|---|
| 31x320 | open position | G, root position | Fb | 1 open string |
| 3x2320 | open position | G, root position | Fb | 1 open string |
| 345353 | 3rd fret | G, root position | G | barred |
| xx5656 | 5th fret | G, root position | Bb | all fretted |
| xx8989 | 8th fret | Bb, 1st inversion | Db | all fretted |
| x-10-11-9-11-9 | 9th fret | G, root position | Db | all fretted |
| x-x-11-12-11-12 | 11th fret | Db, 2nd inversion | Fb | all fretted |
| 15-x-14-15-14-15 | 14th fret | G, root position | G | barred |
The same notes rebuilt from scratch give 14 drop 2, 10 drop 3 and 1 open string voicings, each on its own page.
Tensions. A shell of Gdim7, root, third and seventh, leaves a string free, and the tones that belong over it are the 9 (A), the 11 (C), the b13 (Eb) and the maj7 (F#).
How to use Gdim7
A diminished seventh divides the octave evenly, so Gdim7 has no single root and no single destination: it can lead to C or to Ab, and it is the same four notes either way.
What to play over Gdim7
Every note of Gdim7 is in G diminished and G half-whole diminished.
Chords near Gdim7
Change one note of Gdim7 and you have Gdim (drop the sixth), Gm6 (the flat fifth becomes a fifth), Gm7b5 (the sixth becomes a flat seventh) or GmMaj7b5 (the sixth becomes a major seventh).
Gdim7 is a diminished chord — root, minor third, flat fifth. Diminished and half-diminished chords on every root.
On Gdim7’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.