A9b5 guitar chord
The root left to the bass player. Frees a finger for a tension.
- Tap a note to hear it
- Arrows change position
- Fingers, notes or intervals
- Play the chord
About A9b5 — rootless voicings
A9b5 is A, C#, Eb, G and B — A7b5 with the natural ninth added over it.
It sounds sleek and tense. Played as a tritone substitution the ♭5 is the root of the dominant it replaced.
A9b5 notes and formula
| A | C# | Eb | G | B |
|---|---|---|---|---|
| 1 | 3 | ♭5 | ♭7 | 9 |
Altered dominant — commonly the tritone substitute.
Also written A9(b5), A9-5 or A9♭5. The same chord either way; which spelling you meet depends on who wrote the chart.
How to play A9b5
Leave the root to the bass player. In a band nobody misses it, and the ear supplies it from the guide tones anyway.
The finger it frees goes to a tension, which is why these sound richer than the shape they came from rather than thinner.
A9b5 has 13 of them, on the middle four strings, the top four strings and strings 5-3-2-1, from open position up to the 12th — every inversion the chord has: C# in the bass, Eb in the bass, G in the bass and B in the bass. The one to learn first is the B shape at the nut, which is the easiest grip here.
5 of them sit on the middle four strings, 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 x01423 — no barre and 1 open string. 1 of the 6 shapes here sits in open position. 2 of the 6 need a barre. Together they cover the neck from the 1st fret to the 12th.
| Frets | Where | Bass | Top | Hand |
|---|---|---|---|---|
| x01423 | open position | A, root position | G | 1 open string |
| 545445 | 4th fret | A, root position | A | barred |
| 5656x7 | 5th fret | A, root position | B | all fretted |
| x67687 | 6th fret | Eb, 2nd inversion | B | all fretted |
| x09889 | 8th fret | A, root position | C# | 1 open string |
| x-12-11-12-12-11 | 11th fret | A, root position | Eb | barred |
The same notes rebuilt from scratch give 9 shell and 1 open string voicings, each on its own page.
Tensions. A shell of A9b5, root, third and seventh, leaves a string free, and the tones that belong over it are the b13 (F) and the 13 (F#).
How to use A9b5
A9b5 is a dominant with its tension raised, so it still points at D — harder than a plain seventh does, because the altered tones sit a semitone from where they are going.
Voice by voice, A9b5 → D. 3 voices move by a semitone, and one note is common to both chords.
| In A9b5 | Moves | In D |
|---|---|---|
| A, the root | stays where it is | A, the fifth |
| C#, the major third | rises a semitone | D, the root |
| Eb, the flat fifth | falls a semitone | D, the root |
| G, the flat seventh | falls a semitone | F#, the major third |
| B, the ninth | falls a whole tone | A, the fifth |
What to play over A9b5
Every note of A9b5 is in A whole tone and A lydian dominant.
Chords near A9b5
Change one note of A9b5 and you have A7b5 (drop the ninth), A9 (the flat fifth becomes a fifth), Aaug9 (the flat fifth becomes a sharp fifth) or A9#11 (add the fifth).
A9b5 is an altered chord — a dominant seventh with its fifth or ninth moved. Altered dominant chords on every root.
On A9b5’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.