F#7b9 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.
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About F#7b9 — shell voicings
F#7b9 is F#, A#, C#, E and G — F#9 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.
F#7b9 notes and formula
| F# | A# | C# | E | G |
|---|---|---|---|---|
| 1 | 3 | 5 | ♭7 | ♭9 |
Altered dominant — it points at a minor chord.
Also written F#7(b9), F#7-9 or F#7♭9. The same chord either way; which spelling you meet depends on who wrote the chart.
How to play F#7b9
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.
F#7b9 has 4 of them, on the bottom four strings, the top four strings and the middle four strings, from open position up to the 12th — all in one inversion, so the bass note never moves. The one to learn first is the F# shape at the nut, which is the easiest grip here.
Start with xx2323 — no barre and down at the nut. 1 of the 7 shapes here sits in open position. 4 of the 7 need a barre. Together they cover the neck from the 1st fret to the 15th.
| Frets | Where | Bass | Top | Hand |
|---|---|---|---|---|
| 212020 | open position | F#, root position | E | barred |
| xx2323 | 2nd fret | E, 3rd inversion | G | all fretted |
| 242323 | 2nd fret | F#, root position | G | barred |
| xx4353 | 3rd fret | F#, root position | G | all fretted |
| x98989 | 8th fret | F#, root position | C# | barred |
| 14-13-14-12-x-x | 12th fret | F#, root position | G | all fretted |
| 14-x-14-15-14-15 | 14th fret | F#, root position | G | barred |
The same notes rebuilt from scratch give 13 drop 2, 8 drop 3, 15 rootless and 5 open string voicings, each on its own page.
Tensions. A shell of F#7b9, root, third and seventh, leaves a string free, and the tones that belong over it are the #11 (B#), the b13 (D) and the 13 (D#).
How to use F#7b9
F#7b9 is a dominant with its tension raised, so it still points at B — harder than a plain seventh does, because the altered tones sit a semitone from where they are going.
Voice by voice, F#7b9 → Bm. 3 voices move by a semitone, and one note is common to both chords.
| In F#7b9 | Moves | In Bm |
|---|---|---|
| F#, the root | stays where it is | F#, the fifth |
| A#, the major third | rises a semitone | B, the root |
| C#, the fifth | rises a semitone | D, the minor third |
| E, the flat seventh | falls a whole tone | D, the minor third |
| G, the flat ninth | falls a semitone | F#, the fifth |
What to play over F#7b9
Every note of F#7b9 is in F# half-whole diminished.
Chords near F#7b9
Change one note of F#7b9 and you have F#7 (drop the flat ninth), F#alt (the fifth becomes a sharp fifth), F#9 (the flat ninth becomes a ninth) or F#7#9 (the flat ninth becomes a minor third).
F#7b9 is an altered chord — a dominant seventh with its fifth or ninth moved. Altered dominant chords on every root.
On F#7b9’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.