What notes are in a C half-diminished chord?

C half-diminished contains four notes: C (root), E♭ (minor third), G♭ (diminished fifth), and B♭ (minor seventh).

How is half-diminished different from fully diminished?

Both share the diminished triad below (root, ♭3, ♭5). The difference is the seventh: half-diminished uses a minor 7th (B♭ from C); fully diminished uses a diminished 7th (B𝄫 / A from C).

What does the ø symbol mean?

ø is the standard chord-symbol notation for half-diminished. Cø7 = Cm7♭5 = "C half-diminished seventh." Some writers use the ø without the 7 implied.

Where does C half-diminished appear in music?

In every B♭-minor jazz standard ("Autumn Leaves," "Stella by Starlight," etc.) as the iiø7 chord. In classical literature, the Tristan chord (Wagner's most famous opening) is essentially a half-diminished sonority transposed.

C half-diminished chord — notes, intervals, and practice

C half-diminished (Cm7♭5 or Cø) — C, E♭, G♭, B♭ — is the iiø7 chord of B♭ minor and a centrepiece of jazz minor-key harmony. The chord stacks two minor thirds and a major third, distinguishing it from the fully-symmetric diminished 7th. It's one of the most evocative four-note sonorities in tonal music.

Intervals

The C half-diminished chord stacks two thirds on the root. Each interval and its size in semitones:

C→Ebminor 3rd3 semitones
Eb→Gbminor 3rd3 semitones
Gb→Bbmajor 3rd4 semitones

On the keyboard

Each note of the C half-diminished chord highlighted on a piano. Pitch class is what matters — any octave works.

On the guitar

One voicing of the C half-diminished chord on a six-string guitar fretboard.

Common mistakes

The seventh is B♭ (a minor 7th from C), not B natural (which would be a major 7th, making this a different chord — C°maj7, virtually never used). The "half" in half-diminished refers to the upper interval being a minor 7th rather than the diminished 7th of the fully-diminished chord. C°7 has B𝄫; Cm7♭5 has B♭.

In context

Cm7♭5 → F7 → B♭m is the textbook ii–V–i in B♭ minor — one of the most-used cadences in jazz. Standards like "Autumn Leaves" and "Blue Bossa" use exactly this pattern at every minor-key turnaround. The chord also appears as a colour chord in late-Romantic music, where its instability invites slow chromatic resolution.

Drill it

The C half-diminished chord is one of 48 in the Chord Trainer. Open the full trainer to practice it alongside related chords with timing and best-time tracking.

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Frequently asked

What notes are in a C half-diminished chord?: C half-diminished contains four notes: C (root), E♭ (minor third), G♭ (diminished fifth), and B♭ (minor seventh).
How is half-diminished different from fully diminished?: Both share the diminished triad below (root, ♭3, ♭5). The difference is the seventh: half-diminished uses a minor 7th (B♭ from C); fully diminished uses a diminished 7th (B𝄫 / A from C).
What does the ø symbol mean?: ø is the standard chord-symbol notation for half-diminished. Cø7 = Cm7♭5 = "C half-diminished seventh." Some writers use the ø without the 7 implied.
Where does C half-diminished appear in music?: In every B♭-minor jazz standard ("Autumn Leaves," "Stella by Starlight," etc.) as the iiø7 chord. In classical literature, the Tristan chord (Wagner's most famous opening) is essentially a half-diminished sonority transposed.