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 | white | thumb (1) | little finger (5) |
| D | white | index finger (2) | middle finger (3) |
| F | white | middle finger (3) | index finger (2) |
| A | white | little finger (5) | thumb (1) |
Right hand: thumb (1) on B, index finger (2) on D, middle finger (3) on F, little finger (5) on A.
Left hand: little finger (5) on B, middle finger (3) on D, index finger (2) on F, thumb (1) on A.
B Half Diminished Inversions
- Root positionB – D – F – A
- 1st inversion (Bm7♭5/D)D – F – A – B
- 2nd inversion (Bm7♭5/F)F – A – B – D
- 3rd inversion (Bm7♭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
- C Major (viiø7)
- A Minor (iiø7)
- D Dorian (vi°)
- E Phrygian (v°)
- F Lydian (#iv°)
- G Mixolydian (iii°)
- A Aeolian (ii°)
- B 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 notes are in Bm7♭5?
How do you play Bm7♭5 on piano?
What are the inversions of Bm7♭5?
What keys contain Bm7♭5?
What is the difference between Bm7♭5 and Bdim?
What is an easy Bm7♭5 for small hands?
What are the frequencies of Bm7♭5?
What is the set class of Bm7♭5?
How do I transpose Bm7♭5 to another key?
Is C♭m7♭5 the same as Bm7♭5?
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 | B3 D4 F4 A4 | 10 | 138 mm | none | identical | |
| Close, first inversion | D4 F4 A4 B4 | 9 | 124 mm | none | identical | |
| Close, second inversion | F4 A4 B4 D5 | 9 | 124 mm | none | identical | |
| Close, third inversion | A4 B4 D5 F5 | 8 | 110 mm | none | identical | |
| Drop 2 | F3 B3 D4 A4 | 16 | 220 mm | none | identical | |
| Drop 3 | D3 B3 F4 A4 | 19 | 261 mm | none | identical | |
| Drop 2 and 4 | B2 F3 D4 A4 | 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 | B2 A3 D4 | 15 | 206 mm | omits F | subset | |
| Guide tones, ♭3 and ♭7 | D4 A4 | 7 | 96 mm | omits B and F | subset | |
| Rootless close | D4 F4 A4 | 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 | B3, D4, F4, A4 | 7 | 10 | 138 mm |
| First inversion: Bm7♭5/D | D | D4, F4, A4, B4 | 6/5 | 9 | 124 mm |
| Second inversion: Bm7♭5/F | F | F4, A4, B4, D5 | 4/3 | 9 | 124 mm |
| Third inversion: Bm7♭5/A | A | A4, B4, D5, F5 | 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 |
|---|---|---|---|---|
| vii, I | C major | viim7♭5 | Bm7♭5 to Cmaj7 | Bm7♭5 opens the phrase |
| ii, v, i | A minor | iim7♭5 | Bm7♭5 to Em7 to Am7 | Bm7♭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 |
|---|---|---|
| C major | viim7♭5 | Dominant function |
| A minor | iim7♭5 | Predominant |
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 |
|---|---|---|---|
| Bdim | drops A | 1 ♭3 ♭5 | 3 |
| Bm7 | F becomes F♯ | 1 ♭3 5 ♭7 | 3 |
| Bdim7 | A becomes A♭ | 1 ♭3 ♭5 ♭♭7 | 3 |
| Bm9 | F becomes F♯, C♯ | 1 ♭3 5 ♭7 9 | 3 |
| Bm | F, A becomes F♯ | 1 ♭3 5 | 2 |
| B7 | D, F becomes D♯, F♯ | 1 3 5 ♭7 | 2 |
| BmMaj7 | F, A becomes F♯, A♯ | 1 ♭3 5 7 | 2 |
| Baug7 | D, F becomes D♯, F× | 1 3 ♯5 ♭7 | 2 |
| B7sus4 | D, F becomes E, F♯ | 1 4 5 ♭7 | 2 |
| Bm6 | F, A becomes F♯, G♯ | 1 ♭3 5 6 | 2 |
Frequencies
| Note | MIDI | Frequency |
|---|---|---|
| B3 | 59 | 246.94 Hz |
| D4 | 62 | 293.66 Hz |
| F4 | 65 | 349.23 Hz |
| A4 | 69 | 440.00 Hz |
Reference pitch A440, 12-TET, close root position.
Set theory: prime form, Forte number, interval vector
- Absolute pitch class set
- {11, 2, 5, 9}
- Normal order
- [9, 11, 2, 5]
- 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.