The B-flat half-diminished seventh chord (abbreviated "Bbm7(b5) chord") is a four-note chord consisting of the notes B♭, D♭, F♭, and A♭. The chord is formed by lowering the fifth of a B-flat minor seventh chord a half step.
B-flat half-diminished seventh chord
B-flat half-diminished chord B-flat minor seventh flat five chord
B♭ D♭ F♭ A♭
1 ♭3 ♭5 ♭7
B♭ø B♭ø7 B♭m7b5 B♭–7(b5) B♭mi7(b5) B♭min7(b5)
tetrad (four-note chord)