Learn › A Flat Diminished Chord on Piano (Abdim)
New Released in April 2026
A Flat Diminished Chord on Piano (Abdim)
The A flat diminished chord (Abdim) on the piano has three notes: Ab, Cb, Ebb. It is a minor triad with a lowered fifth, formula 1 b3 b5, built from two minor thirds. Here is where Abdim comes from, where it resolves and how to play it with both hands.
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- MIDI keyboard
- Digital or acoustic piano
- Guitar
- Computer, phone or tablet
Where Abdim goes
- Abdim is the vii° chord of A major (as G#dim) and the ii° chord of F# minor (as G#dim).
- It wants to move up a semitone: Abdim (G#dim) → A / Am, the bottom note rising to the new root.
- Add Gb and you get Abm7b5 (half-diminished); add Gbb instead and you get Abdim7 (diminished 7th).
How to play Abdim on the piano
Thumb, middle and little finger in the right hand: 1-3-5.
Root position: Ab Cb Ebb
1st inversion: Cb Ebb Ab
2nd inversion: Ebb Ab Cb
- Root position: starts on Ab, a black key; black keys: Ab
- 1st inversion: starts on Cb, a white key; black keys: Ab
- 2nd inversion: starts on Ebb, a white key; black keys: Ab
Make Abdim automatic
ChordRunner mixes Abdim with the chords around it and checks every note you play. MIDI keyboard or microphone, both work.
Play the demoCommon questions
How do you play Abdim on the piano?
Press Ab, Cb, Ebb together: right hand 1-3-5 with the thumb on Ab, left hand 5-3-1 with the little finger on Ab.
What is the difference between Abdim and Abm?
One note. Abm has Eb on top; Abdim moves it to Ebb. The new fifth is what gives Abdim its tense sound.
Where does Abdim go?
Abdim is the vii° chord of A major (as G#dim) and the ii° chord of F# minor (as G#dim). It wants to move up a semitone: Abdim (G#dim) → A / Am, the bottom note rising to the new root.
Can I practise Abdim with a MIDI keyboard or microphone?
Yes. ChordRunner detects a USB MIDI keyboard automatically and also hears an acoustic piano through the microphone. Abdim counts in any position, as long as Ab, Cb, Ebb sound together.
Your instrument is the controller.
ChordRunner is a browser game that teaches piano and guitar chords: a chord appears on screen, you play it on a real instrument, and your runner jumps. MIDI keyboard or microphone, both work.
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