Chord & FretBb7(b5) — dominant seventh flat five
Also written A#7(b5) — the same chord, spelled the other way.
Notes in Bb7(b5): Bb – D – Fb – AbFormula: 1 – 3 – b5 – b7In the formula, the numbers count steps of the major scale starting from the note that names the chord; "b" lowers a half step, "#" raises one — and a slash names the bass note.
Here the fifth drops a semitone and the chord turns ambiguous on purpose: the same four notes serve two distant dominants (C7(b5) and F#7(b5)). That coincidence is the door to the tritone substitution.
The same chord on all four instruments
Where to use it: Jazz, bossa and turnarounds — the natural step toward swapping one dominant for another.
Every region of the neck hides more shapes of Bb7(b5). In Chord & Fret, you hear every shape strummed string by string, in each instrument's own voice; compare positions with their difficulty marked; and set a capo — the diagrams redraw above it. Start free. Unlock everything with Pro. Plays offline.
See the whole neck in Chord & Fret →Part of the Sevenths family.