Adim7

Adim7 is A, C, Eb and Gb, a diminished seventh. The shape this page opens on is written x01212, lowest string first.

Note by note. A is the root, C is the minor third, Eb is the flat fifth and Gb is the diminished seventh.

Also written A°7, Ao7 or A diminished 7. The same chord either way; which spelling you meet depends on who wrote the chart.

There are 8 common shapes for Adim7 on the guitar, and 29 derived voicings in 4 families.

One note away. Change a single note of Adim7 and you have Adim (with one note taken away), Am6 (with one note moved), Am7b5 (with one note moved), AmMaj7b5 (with one note moved) or Am/F# (with one note moved).

The common shapes, written lowest string first: x01212, xx1212, 5x4545, 567575, xx7878, x-x-10-11-10-11, x-12-13-11-13-11, x-x-13-14-13-14.

Under the hand. 1 of the 8 shapes here sits in open position, and the first uses 1 open string with 1 left unplayed. 2 of the 8 need a barre. Together they cover the neck from the 1st fret to the 14th.

Where it goes. A diminished seventh divides the octave evenly, so Adim7 has no single root and no single destination: it can lead to D or to Bb, and it is the same four notes either way.

Shell. 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. Adim7 has x0454x, 5x454x, x-12-x-11-13-11, 5348xx, 5-9-10-8-x-x.

Drop 2. A close-position chord with the second voice from the top lowered an octave. Sits on four adjacent strings. Adim7 has xx1212, 2312xx, x3424x, xx4545, 5645xx, x6757x, xx7878, 8978xx.

Drop 3. The third voice from the top lowered an octave. The dropped voice becomes the bass, which is why a string is skipped. Adim7 has 2x121x, x3x242, 5x454x, x6x575, 8x787x, x-9-x-8-10-8, 11-x-10-11-10-x, x-12-x-11-13-11.

Open string. An open string left ringing against a fretted grip. Because it costs no finger, it sounds a note the closed shape has none left for -- a tension on top, or a pedal root underneath. Either a familiar grip with open strings added, or a shape so sparse the open strings carry the chord. These belong to their key rather than to a shape, so D, A, G and E have many and Eb a handful. Adim7 has 56450x.

Tensions. A shell of Adim7, root, third and seventh, leaves a string free, and the tones that belong over it are the 9 (B), the 11 (D), the b13 (F) and the maj7 (G#).

What kind of chord this is. Adim7 is a diminished chord — root, minor third, flat fifth. diminished and half-diminished chords on every root, and what they are for.

The common shapes and the derived voicings come from different places, and both are explained in where the chords and the theory come from.