Gdim piano chord, G diminished notes and fingering.

The Gdim piano chord is G diminished: the notes G, Bb and Db. It is two minor thirds stacked on top of each other. G up to Bb is three semitones, and Bb up to Db is three more, so the fifth (Db) is lowered to six semitones above the root. Chord charts write it as Gdim or G°.

How to play Gdim on piano

1. Find G on the keyboard. G is the white key between the first and second black keys of the group of three.
2. With your right hand, put finger 1 on G, finger 3 on Bb and finger 5 on Db. Finger 1 is the thumb.
3. Press all three keys together. In root position they run from G3 to Db4, a reach of 6 semitones. Play chord sounds them together and Arpeggio sounds them one by one, from the bottom up.
4. Click Left hand to see the left hand. It plays G2 to Db3, one octave lower: G with finger 5, Bb with finger 3, Db with finger 1.
5. The cards under the keyboard hold the three positions, with G, Bb and Db at the bottom in turn. Play and Arpeggio on a card play that position.
6. Open Note names. As written the keys read G, Bb and Db. Sharps shows G, A# and C#, and Flats shows G, Bb and Db. This chord is written with flats, so As written and Flats match.

How Gdim is built

Counted from the root, the formula is 0, 3, 6. Stacked on each other the gaps are 3 + 3: two minor thirds. Compare it with G minor (G, Bb and D): the first two notes are the same, and the fifth is lowered one semitone from D to Db. A perfect fifth is seven semitones; this one is six, and six semitones is a tritone.

Worked example: the pitch of G3. On a piano tuned to A4 = 440 Hz, a note 14 semitones below A4 has the frequency 440 × 2^(-14/12), which is about 196.00 Hz. Bb3 is 11 semitones below A4, so 440 × 2^(-11/12) gives about 233.08 Hz.

What the keys look like under your hand

G has a black key on each side, F# on its left and Ab on its right. Two of the three notes are black keys (Bb and Db) and one is a white key (G). Your little finger plays Db, a black key with C and D beside it. The little finger is short, so let the hand lean a little toward its edge and aim for the middle of the key. Finger 3 presses Bb, a black key between A and B. The middle fingers are the longest, so they reach black keys most easily.

Gdim inversions and fingering

Gdim has three positions. In root position G is at the bottom. In the first inversion, Bb is at the bottom and the chord is written Gdim/Bb. In the second inversion, Db is at the bottom and the chord is written Gdim/Db. The tightest reach, 6 semitones from the lowest key to the highest, is the root position. The widest, at 9, is the first inversion and second inversion.

The keys that hold Gdim

Gdim fits two of the major and natural minor keys that have a standard key signature, which means every note of it comes from that key's scale. The simplest is Ab major, with 4 flats, where it is chord vii°.

Progressions that use Gdim, with the chord numbers and the chords in that key:

• Ab major: IV-vii°-iii-vi, which is Db, Gdim, Cm, Fm, a run of falling fifths.
• F minor: ii°-v-i, which is Gdim, Cm, Fm, the minor ii-V-i, with the natural minor v.
• Ab major: vii°-I, which is Gdim, Ab, the diminished chord leading up to the tonic.

Here is a worked example in Ab major. The chord before Gdim in the first progression above is Db (Db, F and Ab). From Db in root position, the closest way to reach Gdim is its second inversion (Db, G and Bb, lowest note first): one note stays where it is, and the others move 4 semitones in total, counting each note against the note in the same place from the bottom.

Gdim also sits inside Eb7 (Eb, G, Bb and Db): take the root off that dominant 7th and the notes left over are G, Bb and Db.

What Gdim sounds like

A diminished triad sounds tense and unresolved. It rarely sits still: the usual move is up a semitone to the chord built on Ab. It is used as a passing chord between two others and as a spice inside a progression.

Gdim is the vii° chord in Ab major and the ii° chord in F minor. It is also chord vii° of Ab minor, using the raised seventh of the harmonic minor scale.

A common mistake with Gdim

A common mistake is pressing D instead of Db, one semitone higher than the fifth of Gdim. That gives Gm (G, Bb and D), a plain minor chord. The top key of Gdim is a semitone lower than you might expect, so check it against the chord of the same root.

Chords to learn next

Chords close to Gdim: G minor (raises the fifth; shares G and Bb); Eb7 (the dominant 7th it sits inside; contains all its notes); Ab major (the chord it leads to; shares no note); Gm7 (adds a minor seventh to the minor chord; shares G and Bb).

Once Gdim feels easy, play it and then Ab major to hear it resolve upward. For chords beyond these six types, and for guitar and ukulele shapes, use the chord finder. To play along with your computer keys, open the virtual piano. The piano chords page lists all 72 chords.