F#7b5 guitar chord
An open string left ringing against a fretted grip. Because it costs no finger, it sounds a note the closed shape has none left for -- a tension on top, or a pedal root underneath. Either a familiar grip with open strings added, or a shape so sparse the open strings carry the chord. These belong to their key rather than to a shape, so D, A, G and E have many and Eb a handful.
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About F#7b5 — open string voicings
F#7b5 is F#, A#, C and E — F#7 with the fifth lowered a semitone.
It sounds symmetrical and slightly unreal. The same four notes spell a 7♭5 a tritone away, which is exactly why one can stand in for the other.
F#7b5 notes and formula
| F# | A# | C | E |
|---|---|---|---|
| 1 | 3 | ♭5 | ♭7 |
Altered dominant — and the chord that makes the tritone substitution work.
Also written F#7(b5), F#7-5 or F#7♭5. The same chord either way; which spelling you meet depends on who wrote the chart.
How to play F#7b5
An open string left ringing against a fretted grip. It costs no finger, so it can sound a note the closed shape has none left for: a tension on top, or a pedal root underneath.
These belong to their key rather than to a shape: they cannot be moved up the neck. D, A, G and E have many; E♭ has a handful.
F#7b5 has 3 of them, on strings 6-5-4-3-2-1 and the bottom four strings, from the 3rd fret up to the 5th — all in one inversion, so the bass note never moves. The one to learn first is the E shape at the 3rd fret, which is the easiest grip here.
Start with 2x231x — no barre and down at the nut. None of the shapes for F#7b5 uses an open string, so every one of them is movable; the lowest sits at the 1st fret. 1 of the 7 needs a barre. Together they cover the neck from the 1st fret to the 15th.
| Frets | Where | Bass | Top | Hand |
|---|---|---|---|---|
| 2x231x | 1st fret | F#, root position | C | all fretted |
| xx4556 | 4th fret | F#, root position | A# | all fretted |
| x78978 | 7th fret | E, 3rd inversion | C | all fretted |
| xx8978 | 7th fret | A#, 1st inversion | C | all fretted |
| x-9-10-9-11-0 | 9th fret | F#, root position | A# | 1 open string |
| x-9-10-9-11-9 | 9th fret | F#, root position | Db | barred |
| 14-x-14-15-13-x | 13th fret | F#, root position | C | all fretted |
The same notes rebuilt from scratch give 6 shell, 14 drop 2 and 9 drop 3 voicings, each on its own page.
Tensions. A shell of F#7b5, root, third and seventh, leaves a string free, and the tones that belong over it are the b9 (G), the 9 (G#), the #9 (G##), the b13 (D) and the 13 (D#).
How to use F#7b5
F#7b5 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#7b5 → B. 3 voices move by a semitone, and one note is common to both chords.
| In F#7b5 | Moves | In B |
|---|---|---|
| F#, the root | stays where it is | F#, the fifth |
| A#, the major third | rises a semitone | B, the root |
| C, the flat fifth | falls a semitone | B, the root |
| E, the flat seventh | falls a semitone | D#, the major third |
What to play over F#7b5
Every note of F#7b5 is in F# whole tone, F# lydian dominant, F# altered and F# half-whole diminished.
Chords near F#7b5
Change one note of F#7b5 and you have F#maj7b5 (the flat seventh becomes a major seventh), F#m7b5 (the major third becomes a minor third), F#7 (the flat fifth becomes a fifth), F#aug7 (the flat fifth becomes a sharp fifth) or F#9b5 (add the ninth).
F#7b5 is an altered chord — a dominant seventh with its fifth or ninth moved. Altered dominant chords on every root.
On F#7b5’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.