Root, third and seventh: the guide tones fix the quality, so the fifth is dropped. That is what leaves a string free, so pick a tension to put on top.
D7b9 is D, F#, A, C and Eb — D9 with the ninth lowered a semitone.
It sounds dark and urgent. The flat ninth comes from the harmonic minor, so this is the V of a minor key rather than a major one.

| D | F# | A | C | Eb |
|---|---|---|---|---|
| 1 | 3 | 5 | ♭7 | ♭9 |
Altered dominant — it points at a minor chord.
Also written D7(b9), D7-9 or D7♭9. The same chord either way; which spelling you meet depends on who wrote the chart.
Root, third and seventh. The third and seventh, the guide tones, are what make the chord major, minor or dominant, so the fifth can go: it says nothing the symbol needs.
Three notes means a spare string, which is the real point. Put a tension on it.
D7b9 has 3 of them, on the middle four strings, the bottom four strings and the top four strings, from the 4th fret up to the 11th — all in one inversion, so the bass note never moves. The one to learn first is the D shape at the 4th fret, which is the easiest grip here.
Start with xx0542 — no barre and 1 open string. 1 of the 7 shapes here sits in open position. 2 of the 7 need a barre. Together they cover the neck from the 2nd fret to the 13th.
| Frets | Where | Bass | Top | Hand |
|---|---|---|---|---|
| xx0542 | open position | D, root position | F# | 1 open string |
| x54545 | 4th fret | D, root position | A | barred |
| x60575 | 5th fret | Eb, 9th in the bass | A | 1 open string |
| 10-9-10-8-x-x | 8th fret | D, root position | Eb | all fretted |
| x-x-10-11-10-11 | 10th fret | C, 3rd inversion | Eb | all fretted |
| 10-12-10-11-10-11 | 10th fret | D, root position | Eb | barred |
| x-x-12-11-13-11 | 11th fret | D, root position | Eb | all fretted |
The same notes rebuilt from scratch give 12 drop 2, 8 drop 3 and 13 rootless voicings, each on its own page.
Tensions. A shell of D7b9, root, third and seventh, leaves a string free, and the tones that belong over it are the #11 (G#), the b13 (Bb) and the 13 (B).
D7b9 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, D7b9 → Gm. 3 voices move by a semitone, and one note is common to both chords.
| In D7b9 | Moves | In Gm |
|---|---|---|
| D, the root | stays where it is | D, the fifth |
| F#, the major third | rises a semitone | G, the root |
| A, the fifth | rises a semitone | Bb, the minor third |
| C, the flat seventh | falls a whole tone | Bb, the minor third |
| Eb, the flat ninth | falls a semitone | D, the fifth |
Every note of D7b9 is in D half-whole diminished.
Change one note of D7b9 and you have D7 (drop the flat ninth), Dalt (the fifth becomes a sharp fifth), D9 (the flat ninth becomes a ninth), D7#9 (the flat ninth becomes a minor third) or D/C (drop the flat ninth).
D7b9 is an altered chord — a dominant seventh with its fifth or ninth moved. Altered dominant chords on every root.
On D7b9’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.