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C♯ minor 7th flat 5th chord on bass (C♯m7♭5)
Also called or written C♯m7♭5, C♯ or C♯ Half Diminished Minor 7
C♯ minor 7th flat 5th contains C♯, E, G and B. The 9th-fret shape spreads four fingers across two frets, demanding a wide left-hand stretch.
How it is built
Formula 1, ♭3, ♭5, ♭7
How do you play a C♯ minor 7th flat 5th chord on bass?
C♯ minor 7th flat 5th is played at the 9th fret as 9 10 9 9: index finger on the E string at fret 9, pinky finger on the A string at fret 10, middle finger on the D string at fret 9 and ring finger on the G string at fret 9.
Full note and interval breakdown
| String | Fret | Finger | Note |
|---|---|---|---|
| 4 (E) | 9 | 1 | C♯ (1) |
| 3 (A) | 10 | 4 | G (♭5) |
| 2 (D) | 9 | 2 | B (♭7) |
| 1 (G) | 9 | 3 | E (♭3) |
AdvancedThe wide stretch between the index finger on the 4th string and the pinky on the 3rd string at the 9th fret is the hardest part.
C♯m7♭5/G inversion
C♯ minor 7th flat 5th is played at the 2nd fret as 3 4 2 4: middle finger on the E string at fret 3, ring finger on the A string at fret 4, index finger on the D string at fret 2 and pinky finger on the G string at fret 4.
Full note and interval breakdown
| String | Fret | Finger | Note |
|---|---|---|---|
| 4 (E) | 3 | 2 | G (♭5) |
| 3 (A) | 4 | 3 | C♯ (1) |
| 2 (D) | 2 | 1 | E (♭3) |
| 1 (G) | 4 | 4 | B (♭7) |
C♯m7♭5/B inversion
C♯ minor 7th flat 5th is played at the 5th fret as 7 7 5 6: ring finger on the E string at fret 7, pinky finger on the A string at fret 7, index finger on the D string at fret 5 and middle finger on the G string at fret 6.
Full note and interval breakdown
| String | Fret | Finger | Note |
|---|---|---|---|
| 4 (E) | 7 | 3 | B (♭7) |
| 3 (A) | 7 | 4 | E (♭3) |
| 2 (D) | 5 | 1 | G (♭5) |
| 1 (G) | 6 | 2 | C♯ (1) |
Why it sounds like that
C♯ minor 7th flat 5th is built from the formula 1, ♭3, ♭5, ♭7. The diminished 5th between C♯ and G gives the chord its tense, unresolved quality. Raising the ♭5 to a perfect 5th produces C♯ minor 7th, the closest stable contrast.
What goes wrong with C♯ minor 7th flat 5th?
- Letting the pinky collapse and mute the 2nd string.
- Fretting the 1st string with the ring finger too far from the fret, causing a buzz.
- Allowing the index finger to touch the 3rd string and deaden the C♯.
When to use it
C♯ minor 7th flat 5th functions as the ii chord in B natural minor and the vii chord in D major. Use it in minor-key jazz and blues lines where the half-diminished colour leads to a dominant. It pairs naturally with C♯ minor and C♯ 5th.
Changing to and from C♯ minor 7th flat 5th
- Sliding the shape down one fret to the 8th fret gives C minor 7th flat 5th.
- Sliding the shape up one fret to the 10th fret gives D minor 7th flat 5th.
Which voicing to use
The 9th-fret root position keeps C♯ in the bass for a grounded sound. The C♯m7♭5/G inversion at the 3rd fret places the diminished 5th in the bass, creating a darker, less stable feel. Choose the C♯m7♭5/B inversion when the bass line needs to descend to B.
Other C♯ chords
Common questions
How is C♯ minor 7th flat 5th written?
C♯ minor 7th flat 5th is written as C♯m7♭5, and it is also called Half Diminished Minor 7. The ASCII root spelling is C#. It is also spelled D♭ in enharmonic notation for the same sounding root.
What is the difference between C♯ minor 7th flat 5th and C♯ diminished?
C♯ minor 7th flat 5th adds a minor 7th to the diminished triad. C♯ diminished has only the root, ♭3 and ♭5.
Why does C♯ minor 7th flat 5th sound unstable?
The tritone between C♯ and G creates tension that wants to resolve. This instability makes the chord useful as a passing harmony.