Construction
| Note | Interval | Degree |
|---|---|---|
| B♭ | Root | 1 |
| D♭ | Minor 3rd | ♭3 |
| F♭ | Diminished 5th | ♭5 |
| A♭ | Minor 7th | ♭7 |
Fingering
| Note | Key color | Right hand | Left hand |
|---|---|---|---|
| B♭ | black | index finger (2) | little finger (5) |
| D♭ | black | middle finger (3) | ring finger (4) |
| F♭ | white | ring finger (4) | middle finger (3) |
| A♭ | black | little finger (5) | index finger (2) |
Right hand: index finger (2) on B♭, middle finger (3) on D♭, ring finger (4) on F♭, little finger (5) on A♭.
Left hand: little finger (5) on B♭, ring finger (4) on D♭, middle finger (3) on F♭, index finger (2) on A♭.
B♭ Half Diminished Inversions
- Root positionB♭ – D♭ – F♭ – A♭
- 1st inversion (B♭m7♭5/D♭)D♭ – F♭ – A♭ – B♭
- 2nd inversion (B♭m7♭5/F♭)F♭ – A♭ – B♭ – D♭
- 3rd inversion (B♭m7♭5/A♭)A♭ – B♭ – D♭ – F♭
Key Signature
A Half Diminished chord is built from symmetrical or ambiguous intervals, so it doesn't belong to a single key and has no key signature of its own.
Chords in the Key of B♭ Major
These are the triads built on each degree of B♭ Major:
How B♭ Half Diminished functions in a key
The same chord takes on a different harmonic role depending on the key it appears in. Here is where B♭ Half Diminished sits diatonically across the common keys:
- In C♭ major, B♭ Half Diminished is the vii° chord — the dominant.
- In A♭ minor, B♭ Half Diminished is the ii° chord — a predominant.
Scales That Include the B♭ Half Diminished
- B Major (vii⦰7)
- G# Minor (ii⦰7)
- C# Dorian (vi°)
- D# Phrygian (v°)
- E Lydian (#iv°)
- F# Mixolydian (iii°)
- G# Aeolian (ii°)
- A# Locrian (i°)
Same Notes, Other Names
The notes B♭ – D♭ – F♭ – A♭ aren’t exclusive to this chord. Depending on which note is the bass and how the chord functions, the same pitches also spell:
B♭ Half Diminished : Frequently Asked Questions
What is the B♭ Half Diminished chord on piano?
What notes are in the Bb Half Diminished chord?
How does Bbm7b5 differ from Bbdim7?
How is Bbm7b5 used?
What songs use Half Diminished?
How does Bbm7b5 differ from Bbm7?
Is Bbm7b5 the same as Dbm6?
B♭ Half Diminished 7th in detail
Exact
Every pitch class is present and nothing outside the chord is added.
| Type | Notes | Semitones | Span | Omissions and additions | Set relation | Fit |
|---|---|---|---|---|---|---|
| Close, root position | B♭3 D♭4 F♭4 A♭4 | 10 | 138 mm | none | identical | |
| Close, first inversion | D♭4 F♭4 A♭4 B♭4 | 9 | 124 mm | none | identical | |
| Close, second inversion | F♭4 A♭4 B♭4 D♭5 | 9 | 124 mm | none | identical | |
| Close, third inversion | A♭4 B♭4 D♭5 F♭5 | 8 | 110 mm | none | identical | |
| Drop 2 | F♭3 B♭3 D♭4 A♭4 | 16 | 220 mm | none | identical | |
| Drop 3 | D♭3 B♭3 F♭4 A♭4 | 19 | 261 mm | none | identical | |
| Drop 2 and 4 | B♭2 F♭3 D♭4 A♭4 | 22 | 303 mm | none | identical |
Reduced
A subset of the pitch classes: the identity is incomplete rather than altered.
| Type | Notes | Semitones | Span | Omissions and additions | Set relation | Fit |
|---|---|---|---|---|---|---|
| Shell, root ♭7 ♭3 | B♭2 A♭3 D♭4 | 15 | 206 mm | omits F♭ | subset | |
| Guide tones, ♭3 and ♭7 | D♭4 A♭4 | 7 | 96 mm | omits B♭ and F♭ | subset | |
| Rootless close | D♭4 F♭4 A♭4 | 7 | 96 mm | omits B♭ | subset |
Spans are measured centre to centre at a 165 mm octave (standard keyboard geometry).
| Position | Bass note | Notes in order | Figured bass | Semitones | Span |
|---|---|---|---|---|---|
| Root position | B♭ | B♭3, D♭4, F♭4, A♭4 | 7 | 10 | 138 mm |
| First inversion: B♭m7♭5/D♭ | D♭ | D♭4, F♭4, A♭4, B♭4 | 6/5 | 9 | 124 mm |
| Second inversion: B♭m7♭5/F♭ | F♭ | F♭4, A♭4, B♭4, D♭5 | 4/3 | 9 | 124 mm |
| Third inversion: B♭m7♭5/A♭ | A♭ | A♭4, B♭4, D♭5, F♭5 | 4/2 | 8 | 110 mm |
One position per chord tone in the bass. Spans are for close position: voiced inversions appear under Voicings.
| Progression | Key | Role | Sequence | Voice leading |
|---|---|---|---|---|
| ii, v, i | G♯ minor | iim7♭5 | A♯m7♭5 to D♯m7 to G♯m7 | B♭m7♭5 opens the phrase |
| vii, I | B major | viim7♭5 | A♯m7♭5 to Bmaj7 | B♭m7♭5 opens the phrase |
Root motion, common tones and voice displacement are computed from pitch class sets. Roman numerals follow common practice functional harmony.
Which keys it belongs to
| Key | Roman numeral | Function |
|---|---|---|
| G♯ minor | iim7♭5 | Predominant |
| B major | viim7♭5 | Dominant function |
Classification system: common-practice functional harmony.
Change one note
Chords a single note away, and what moving that note does.
| Chord | Change | Formula | Common tones |
|---|---|---|---|
| B♭dim | drops A♭ | 1 ♭3 ♭5 | 3 |
| B♭m7 | F♭ becomes F | 1 ♭3 5 ♭7 | 3 |
| B♭dim7 | A♭ becomes A♭♭ | 1 ♭3 ♭5 ♭♭7 | 3 |
| B♭m9 | F♭ becomes F, C | 1 ♭3 5 ♭7 9 | 3 |
| B♭m | F♭, A♭ becomes F | 1 ♭3 5 | 2 |
| B♭7 | D♭, F♭ becomes D, F | 1 3 5 ♭7 | 2 |
| B♭mMaj7 | F♭, A♭ becomes F, A | 1 ♭3 5 7 | 2 |
| B♭aug7 | D♭, F♭ becomes D, F♯ | 1 3 ♯5 ♭7 | 2 |
| B♭7sus4 | D♭, F♭ becomes E♭, F | 1 4 5 ♭7 | 2 |
| B♭m6 | F♭, A♭ becomes F, G | 1 ♭3 5 6 | 2 |
Frequencies
| Note | MIDI | Frequency |
|---|---|---|
| B♭3 | 58 | 233.08 Hz |
| D♭4 | 61 | 277.18 Hz |
| F♭4 | 64 | 329.63 Hz |
| A♭4 | 68 | 415.30 Hz |
Reference pitch A440, 12-TET, close root position.
Set theory: prime form, Forte number, interval vector
- Absolute pitch class set
- {10, 1, 4, 8}
- Normal order
- [8, 10, 1, 4]
- Prime form
- (0258)
- Forte number
- 4-27
- Interval vector
- <012111>
| Pair | Interval | Semitones | Interval class |
|---|---|---|---|
| B♭ to D♭ | Minor third | 3 | 3 |
| B♭ to F♭ | Tritone | 6 | 6 |
| B♭ to A♭ | Minor seventh | 10 | 2 |
| D♭ to F♭ | Minor third | 3 | 3 |
| D♭ to A♭ | Perfect fifth | 7 | 5 |
| F♭ to A♭ | Major third | 4 | 4 |
Where these facts come from
Every value on this page is derived from the note formula for a half diminished 7th applied to the root B♭, using standard music theory. Nothing here is hand-entered per chord, so the notes, intervals, inversions and frequencies cannot drift out of agreement with each other. Pitches assume 12-TET at A440.