A#°
Triads · A# root / B♭
A#° / B♭°
A tense, unstable triad built from two stacked minor thirds.
0 st3 st6 st
Notes in A#°
BbRoot
Db3rd
E5th
A# / Bb is a favourite for horn players and jazz musicians. Many blues and jazz standards are in Bb.
Identify the Chord Quality on A#
Each chord below is played on A#. Listen and identify whether you heard A#°, A#m, A#7, 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# (also written B♭°). It contains the notes Bb, Db, E — 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.