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New Released in April 2026

A Diminished Chord on Piano (Adim)

A diminished (Adim) is spelled A - C - Eb: root, minor 3rd and diminished 5th. Its sound is tense, so it rarely stays long before moving on. Below: the keyboard, the three positions, how it compares with A and Am, and where it goes next.

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Adim A C Eb

The A diminished chord and its inversions

Thumb, middle and little finger in the right hand: 1-3-5.

Adim A C Eb

Root position: A C Eb

Adim C Eb A

1st inversion: C Eb A

Adim Eb A C

2nd inversion: Eb A C

  • Root position: starts on A, a white key; black keys: Eb
  • 1st inversion: starts on C, a white key; black keys: Eb
  • 2nd inversion: starts on Eb, a black key; black keys: Eb

Four triads on A

One key changes and the chord changes family.

ChordNotesThirdFifth
A A C# Emajor 3rdperfect 5th
Am A C Eminor 3rdperfect 5th
Adim A C Ebminor 3rddiminished 5th
Aaug A C# E#major 3rdaugmented 5th

What Adim does in music

  • Adim is the vii° chord of Bb major and the ii° chord of G minor.
  • It wants to move up a semitone: Adim → Bb / Bbm, the bottom note rising to the new root.
  • Add G and you get Am7b5 (half-diminished); add Gb instead and you get Adim7 (diminished 7th).

Am7b5 · Bb

ChordRunner showing a chord block while hands play the piano

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In ChordRunner Adim rides towards your runner between other chords: play it in time. MIDI keyboard or microphone, both work.

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All piano chords · Diminished chords explained

Common questions

What notes are in the A diminished chord?

Adim has three notes: A, C, Eb. Root, minor 3rd and diminished 5th (formula 1 b3 b5).

What is the difference between Adim and Am?

One note. Am has E on top; Adim moves it to Eb. The new fifth is what gives Adim its tense sound.

Where does Adim go?

Adim is the vii° chord of Bb major and the ii° chord of G minor. It wants to move up a semitone: Adim → Bb / Bbm, the bottom note rising to the new root.

Can I practise Adim with a MIDI keyboard or microphone?

Yes. ChordRunner detects a USB MIDI keyboard automatically and also hears an acoustic piano through the microphone. Adim counts in any position, as long as A, C, Eb 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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