Bb7b5 keeps the dominant 3rd and flat 7th of , but lowers its 5th to : Bb, D, Fb and Ab.
The flat 5th is the note that names this chord, so let it sound. A sharp 11th is written differently because its natural 5th remains.
Also written Bb7(b5), Bb7-5 or Bb7♭5.
Bb7b5 in 3rd inversion puts Ab in the bass instead of Bb, the 7th of the chord. The notes are the same; what changes is what the bass line does, which is most of why you would reach for it — it lets the lowest voice move by step where the root would have jumped.
One of Bb7b5’s 9 shapes does this:4x233x
Built on the flat sixth of a minor key, Bb7b5 is the classical French sixth under a lead-sheet name, one of the strongest ways into A: its bass falls a half step and its seventh rises a half step, both onto the V’s root. The 7♭5 a tritone away has the same four notes.
Listen for: The seventh rises a half step as the bass falls a half step; they meet on the root of the V, an octave apart.
Heard in“Bernie’s Tune”
Contains Bb7b5 and adds ninth and sharp fifth.
Adds ninth, fifth and thirteenth, for a dominant sharp-eleventh color.
Contains Bb7b5 and adds flat ninth, sharp ninth and sharp fifth.
Contains Bb7b5 and adds flat ninth, sharp ninth, fifth and thirteenth.
The common shapes and the derived voicings come from different places, and both are explained in how this site is built.
Shows each chord the way this style would voice it, and marks which of its alternatives belong to the idiom.