1b3b5
Fig. 1 · Adim on the keyboard

piano chord

Adim

A1C♭3E♭♭5

Two minor thirds stacked. The fifth is diminished, so it cannot be dropped without losing the chord.

on guitaron ukulelethe scale

What is true of it

Adim is A, C and E♭ — 1, b3 and b5 counted from A.

A in other shapes

AmajorAmminorAaugaugmentedA5power chordAsus2suspended secondAsus4suspended fourth

CdimC♯dimD♭dimDdimD♯dimE♭dimEdimFdimall 374