Four notes · 1 ♭3 ♭5 ♭7 · pure 5:6:7:9
The half-diminished chord
A half-diminished chord is a diminished chord with a minor seventh on top, also called minor 7 flat 5. It sounds dark and searching, softer than the full diminished 7th.
How it's built
Stack two minor thirds and a major third: C, E♭, G♭ and B♭. It's half diminished because only the triad is diminished; the seventh is a minor seventh, not a diminished one. Its top three notes make an E♭ minor chord, so Cm7♭5 has the same notes as E♭m6.
Singing it in tune
Switched to Pure, this page tunes it 5:6:7:9. The minor third sits 15.6 cents (a cent is a hundredth of a semitone) above the piano's, the diminished fifth, 7:5, 17.5 below, and the seventh, 9:5, 17.6 above. Between the ♭5 and the seventh is 9:7, a wide major third, 35.1 cents wider than the piano's.
Those are harmonics 5, 6, 7 and 9: a dominant 9th chord, 4:5:6:7:9, with its root left out. B, D, F and A, Bm7♭5, are G9 without the G, which is why the chord so often does a dominant's job.
Where you hear it
On the second note of a minor key, leading to the dominant: Dm7♭5, G7, C minor, the minor ii-V-i of jazz. In a major key it's the chord on the seventh note, Bm7♭5 in C. The opening of Wagner's Tristan und Isolde, from 1859, famously centres on a chord with this sound, F, B, D♯ and G♯, known as the Tristan chord.
More chord types
Free tools by Stackapella
All of these are free, and so is every course.
Stackapella teaches you to sing harmony one part at a time, right in your browser.
- A guide sings your partHear your line over the others, slow it down, then take your turn.
- Your notes light upEach note shows where you landed, and a hint when to go up or down.
- Record every part yourselfStack your takes in time until you're the whole choir.
- Every course free
- Open source
- No ads, no tracking
Questions
Why is it called half-diminished?
Because only half of it is diminished: the triad is, but the seventh is minor. A fully diminished 7th has a diminished seventh as well.
What does ø mean in a chord symbol?
Half-diminished: Cø7, Cø and Cm7♭5 all mean C, E♭, G♭ and B♭.
What is the difference between half-diminished and diminished 7th?
The seventh: a minor seventh in the half-diminished (B♭ over C), a diminished seventh in the diminished 7th (B𝄫, sounding as A). Half-diminished is the darker, gentler of the two.
Is Cm7♭5 the same as E♭m6?
They share the same four notes, C, E♭, G♭ and B♭. With C in the bass it's Cm7♭5; with E♭ there it acts as E♭m6.
More free tools
No account, no ads. Each one keeps working offline once you've opened it.
See all 17 tools