A9b5 guitar chord
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About A9b5 — uncommon voicings
A9b5 is A, C#, Eb, G and B — 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.
Also written A9(b5), A9-5 or A9♭5.
What these less common shapes are
How to use A9b5
A9b5 is a dominant with its tension raised, so it still points at — harder than a plain seventh does. A plain dominant has two voices a semitone from home; an altered one has four, because every altered tone is also sitting a semitone from a note of D. More voices leaning the same way is all "more tension" means here.
In a phrase:→→
The ii–V–I of D.
Voice by voice, A9b5 → . 3 voices move by a semitone, and one note is common to both chords. Those semitones are what the ear follows; the rest is the chord rearranging itself underneath.
| 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.
Each of those is a page: the scale across the neck, and the chords it harmonises into — which is where A9b5 sits in it. Every scale.
Chords near A9b5
Change one note of A9b5 and you have (drop the ninth), (the flat fifth becomes the fifth), (the flat fifth becomes the sharp fifth) or (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.