The third voice from the top lowered an octave. The dropped voice becomes the bass, which is why a string is skipped.
D7b5 is D, F#, Ab and C — D7 with the fifth lowered a semitone.
It sounds symmetrical and slightly unreal. The same four notes spell a 7♭5 a tritone away, which is exactly why one can stand in for the other.

| D | F# | Ab | C |
|---|---|---|---|
| 1 | 3 | ♭5 | ♭7 |
Altered dominant — and the chord that makes the tritone substitution work.
Also written D7(b5), D7-5 or D7♭5. 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.
D7b5 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.
Start with xx0112 — 1 open string and only 3 fretted notes. 1 of the 6 shapes here sits in open position. None of them needs a barre. Together they cover the neck from the 1st fret to the 14th.
| Frets | Where | Bass | Top | Hand |
|---|---|---|---|---|
| xx0112 | open position | D, root position | F# | 1 open string |
| x34534 | 3rd fret | C, 3rd inversion | Ab | all fretted |
| xx4534 | 3rd fret | F#, 1st inversion | Ab | all fretted |
| x5657x | 5th fret | D, root position | F# | all fretted |
| 10-x-10-11-9-x | 9th fret | D, root position | Ab | all fretted |
| x-x-12-13-13-14 | 12th fret | D, root position | F# | all fretted |
The same notes rebuilt from scratch give 5 shell, 14 drop 2 and 3 open string voicings, each on its own page.
Tensions. A shell of D7b5, root, third and seventh, leaves a string free, and the tones that belong over it are the b9 (Eb), the 9 (E), the #9 (E#), the b13 (Bb) and the 13 (B).
D7b5 is a dominant with its tension raised, so it still points at G — harder than a plain seventh does, because the altered tones sit a semitone from where they are going.
Voice by voice, D7b5 → G. 3 voices move by a semitone, and one note is common to both chords.
| In D7b5 | Moves | In G |
|---|---|---|
| D, the root | stays where it is | D, the fifth |
| F#, the major third | rises a semitone | G, the root |
| Ab, the flat fifth | falls a semitone | G, the root |
| C, the flat seventh | falls a semitone | B, the major third |
Every note of D7b5 is in D whole tone, D lydian dominant, D altered and D half-whole diminished.
Change one note of D7b5 and you have Dmaj7b5 (the flat seventh becomes a major seventh), Dm7b5 (the major third becomes a minor third), D7 (the flat fifth becomes a fifth), Daug7 (the flat fifth becomes a sharp fifth), D9b5 (add the ninth) or D/C (the flat fifth becomes a fifth).
D7b5 is an altered chord — a dominant seventh with its fifth or ninth moved. Altered dominant chords on every root.
On D7b5’s sound and use this page follows Mark Levine, The Jazz Theory Book (Sher Music, 1995). The shapes and the derived voicings come from different places, and both are explained in where the chords and the theory come from.
Shows each chord the way this style would voice it, and marks which of its alternatives belong to the idiom.