Chord · Bb Dominant 7♯5
B♭7♯5 Chord
B♭7♯5 is Bb, D, F# and Ab — whole-tone derived; very tense.
B♭7♯5 on every instrument
The same 4 notes, 2 sets of hands. Open a diagram for alternate shapes, audio and the mistakes to avoid.
What B♭7♯5 is made of
Bb Dominant 7♯5 (Bb dominant 7♯5) is built from the notes Bb, D, F#, Ab, with the interval pattern 1, 3, #5, b7. A common dominant 7♯5 chord across many styles.
Stack 1, 3, #5 and b7 on a root of B♭ and you get Bb, D, F# and Ab. That interval recipe is what makes the chord a seventh sharp five chord — move the same shape to another root and the character travels with it, which is why C7♯5 sounds like a transposed B♭7♯5.
Dominant 7♯5: Whole-tone derived; very tense.
Spelling: the notes above are written the way a score would write them, not simplified to the nearest piano key. That is why this chord is spelled with B♭ rather than its enharmonic equivalent.
Keys that contain B♭7♯5
No major or natural-minor key contains all 4 of these notes — this one gets borrowed.
Chords like this one sit outside the diatonic set — they arrive as secondary dominants, borrowed chords or passing harmony. Browse every key to see which progressions pull it in.
Other chords on B♭
Same root, different colour.
The same seventh sharp five shape, moved
The identical interval recipe, built on other roots.
Questions people ask about Bb7#5
- What notes are in the Bb7#5 chord?
- Bb7#5 is made of Bb, D, F# and Ab — the 1, 3, #5 and b7 degrees of a seventh sharp five chord built on Bb.
- What keys use the Bb7#5 chord?
- No major or natural-minor key contains all 4 notes of Bb7#5. Chords like this arrive as borrowed harmony — secondary dominants, harmonic-minor colour, or chromatic passing chords — rather than as one of a key's native chords.
- How do you play Bb7#5 on guitar and piano?
- This page shows Bb7#5 on guitar and piano — 5 voicings in total. Each diagram links to the full instrument page with alternate shapes, audio and common mistakes.
- Is Bb7#5 the same as A#7#5?
- Yes. Bb7#5 and A#7#5 are enharmonic — identical pitches written two different ways. Which spelling you use depends on the key you are in; Bb7#5 is the spelling this site treats as canonical.
Learn the theory behind it
Why B♭7♯5 behaves the way it does — the guides that explain the chord instead of just spelling it.