C Half-Diminished Seventh Chord (Cm7♭5)

1Composition: what it contains

C – E♭ – G♭ – B♭

Symbol

Cm7♭5

Also written

Cm7♭5, Cø, Cø7, C-7♭5, Cmi7(♭5)

Formula

1 ♭3 ♭5 ♭7

2Appearance: diagrams and sound

On the guitar

On the ukulele

On the piano

On the staff

On bass and as an arpeggio

3Indications: what it is used for

The iiø7 chord of a minor key: in a minor ii–V–i it leads to V7(♭9) and then to i. It is also the vii chord of a major key (viiø7), used as a dominant-function chord resolving to I. In jazz it appears in minor ii–V's and as a passing chord; in classical music it is a common pre-dominant. Locrian or Locrian ♮2 is the usual scale. It shares notes with the minor sixth chord built a minor third above its root.

4Dosage: how to practise it

On guitar, learn the shape rooted on the fifth string (the most common), the shape rooted on the sixth string with the fifth string muted, and drop-2 voicings. On piano, play it in all inversions and in the minor ii–V–i progression with smooth voice leading. Practise the minor ii–V–i around the circle of fifths at 70–120 BPM. Arpeggiate 1-♭3-♭5-♭7. Five to ten minutes daily, alternating with the diminished seventh to hear the difference.

5Warnings and common mistakes

Do not confuse m7♭5 (half-diminished) with dim7 (fully diminished): the seventh is minor here and diminished in the dim7. On guitar, check that the fifth is really flat; muscle memory from m7 shapes often keeps a perfect fifth. Do not mix up the symbol ø (half-diminished, slashed circle) with ° (diminished). When improvising, the flat second (♭9) is the avoid note.

6Interactions with chords, scales and keys

Inversions

• Inversion 1 · Cm7♭5/E♭ · E♭ – G♭ – B♭ – C Play
• Inversion 2 · Cm7♭5/G♭ · G♭ – B♭ – C – E♭ Play
• Inversion 3 · Cm7♭5/B♭ · B♭ – C – E♭ – G♭ Play

Scales to play over Cm7♭5

• C Locrian Mode
• C Blues Scale
• C Half-Whole Diminished Scale
• C Altered Scale

Where it appears (keys and Roman numerals)

• viiø7 – Key of C sharp Major
• viiø7 – Key of D flat Major
• iiø7 – Key of A sharp Minor
• iiø7 – Key of B flat Minor

7Other presentations available

The same chord from every note

C♯m7♭5 Dm7♭5 E♭m7♭5 Em7♭5 Fm7♭5 F♯m7♭5 Gm7♭5 A♭m7♭5 Am7♭5 B♭m7♭5 Bm7♭5

Other chords on C

C Cm Cdim Caug Csus2 Csus4 C5 C6 Cm6 C7 Cmaj7 Cm7 Cdim7 Cm(maj7) C7sus4 Cadd9 Cm(add9) C6/9 C9 Cmaj9 Cm9 C11 Cm11 C13 C7♭9 C7♯9 C7♯5 C7♭5