The third voice from the top lowered an octave. The dropped voice becomes the bass, which is why a string is skipped.
Dm7b5 is D, F, Ab and C — Dm7 with the fifth lowered a semitone.
It sounds hollow, and unmistakably going somewhere. It walks straight into an altered dominant, which is where you will nearly always meet it.
Pre-dominant — the ii of a minor key.

| D | F | Ab | C |
|---|---|---|---|
| 1 | ♭3 | ♭5 | ♭7 |
Also written Dø, Dø7, Dm7-5, Dm7(b5) or D half diminished. The same chord either way; which spelling you meet depends on who wrote the chart.
The same operation one voice further down: the third voice from the top falls an octave and becomes the bass.
That leaves a bigger hole under the top three notes, so a string gets skipped: the muted string in the middle is the shape, not a mistake.
Dm7b5 has 10 of them, on strings 6-4-3-2 and strings 5-3-2-1, from open position up to the 13th — every inversion the chord has: D in the bass, F in the bass, Ab in the bass and C in the bass. The one to learn first is the F shape at the nut.
5 of them sit on strings 6-4-3-2, so you can run the inversions up one set without changing strings — which is the whole reason to learn them as a family rather than as separate grips.
Play Dm7b5 as a shell — root, third and seventh — and the spare string takes the 11 (G) or the b13 (Bb).
All 9 common shapes as fret numbers, lowest string first. Hover or tap one to see it drawn.
Dm7b5 is the ii of C minor, which is where it is nearly always found: half-diminished, then an altered dominant, then the minor tonic.
In which keys. Every note of Dm7b5 belongs to C minor (the ii°, the supertonic) and Eb major (the vii°, the leading tone).
Every note of Dm7b5 is in D blues, D locrian, D altered and D half-whole diminished.
Change one note of Dm7b5 and you have Ddim (drop the flat seventh), Ddim7 (the flat seventh becomes the diminished seventh), Dm7 (the flat fifth becomes the fifth), DmMaj7b5 (the flat seventh becomes the major seventh) or D7b5 (the minor third becomes the major third).
Dm7b5 is a diminished chord — root, minor third, flat fifth. Diminished and half-diminished chords on every root.
The common shapes and the derived voicings come from different places, and both are explained in how this site is built.
Shows each chord the way this style would voice it, and marks which of its alternatives belong to the idiom.