Sevenths · A# root / B♭
A#ø7 / B♭ø7
Also called min7♭5. The ii° in minor key ii-V-I progressions.
Notes in A#ø7
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#ø7, A#m, A#7, or another quality — the hardest and most useful ear training skill.
Half Diminished in All 12 Keys
Other Chords in A#
Related Sevenths
About the A#ø7 Chord
The A#ø7 chord is a half diminished chord built on A# (also written B♭ø7). It contains the notes Bb, Db, E, Ab — the root, third, fifth, and seventh.
Also called min7♭5. The ii° in minor key ii-V-I progressions. Practising the A#ø7 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.