An open string left ringing against a fretted grip. Because it costs no finger, it sounds a note the closed shape has none left for -- a tension on top, or a pedal root underneath. Either a familiar grip with open strings added, or a shape so sparse the open strings carry the chord. These belong to their key rather than to a shape, so D, A, G and E have many and Eb a handful.
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.
An open string left ringing against a fretted grip. It costs no finger, so it can sound a note the closed shape has none left for: a tension on top, or a pedal root underneath.
These belong to their key rather than to a shape: they cannot be moved up the neck. D, A, G and E have many; E♭ has a handful.
D7b5 has 3 of them, on strings 6-5-4-3-2-1, strings 5-4-3-2-1 and strings 6-4-3-2-1, from the 3rd fret up to the 5th — every inversion the chord has: D in the bass and Ab in the bass. The one to learn first is the Ab shape at the 4th fret, which is the easiest grip here.
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 10 drop 3 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.