A°
Triads · A root
A°
A tense, unstable triad built from two stacked minor thirds.
0 st3 st6 st
Notes in A°
ARoot
C3rd
D#5th
A is the reference pitch (A440). Very common in rock and pop — the vi chord in C major.
Identify the Chord Quality on A
Each chord below is played on A. Listen and identify whether you heard A°, Am, A7, or another quality — the hardest and most useful ear training skill.
Diminished in All 12 Keys
Other Chords in A
Related Triads
About the A° Chord
The A° chord is a diminished chord built on A. It contains the notes A, C, D# — the root, third, and fifth.
A tense, unstable triad built from two stacked minor thirds. Practising the A° chord across different voicings and contexts builds the harmonic recognition that lets you identify it instantly in any musical setting — whether in a band mix, a recording, or a live performance.