A9b5 guitar chord
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.
- Tap a note to hear it
- Arrows change position
- Fingers, notes or intervals
- Play the chord
About A9b5 — shell 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.
Altered dominant — commonly the tritone substitute.
A9b5 notes and formula
| A | C# | Eb | G | B |
|---|---|---|---|---|
| 1 | 3 | ♭5 | ♭7 | 9 |
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
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.
A9b5 has 9 of them, on the middle four strings, the bottom four strings, the top four strings, strings 6-4-3-2 and strings 5-3-2-1, from the 2nd fret up to the 11th — all in one inversion, so the bass note never moves. The one to learn first is the A shape at the 4th fret, which is the easiest grip here.
Five notes and four fingers, so something has to go. Keep C# and G (they fix the quality) and Eb and B (what the symbol is about). Let A go — a perfect fifth says nothing the root has not, and in a band the bass has the root.
Play A9b5 as a shell — root, third and seventh — and the spare string takes the b13 (F) or the 13 (F#).
All 6 common shapes as fret numbers, lowest string first. Hover or tap one to see it drawn.
- x01423, open position, A, root position, top note G, 1 open string
- 545445, 4th fret, A, root position, top note A, barred
- 5656x7, 5th fret, A, root position, top note B, all fretted
- x67687, 6th fret, Eb, 2nd inversion, top note B, all fretted
- x09889, 8th fret, A, root position, top note C#, 1 open string
- x-12-11-12-12-11, 11th fret, A, root position, top note Eb, barred
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.
In a phrase:Em7→A9b5→Dmaj7— the ii–V–I of D.
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 the fifth), Aaug9 (the flat fifth becomes the 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.
The common shapes and the derived voicings come from different places, and both are explained in how this site is built.