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.
F9b5 is F, A, Cb, Eb and G — F7b5 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.

| F | A | Cb | Eb | G |
|---|---|---|---|---|
| 1 | 3 | ♭5 | ♭7 | 9 |
Altered dominant — commonly the tritone substitute.
Also written F9(b5), F9-5 or F9♭5. The same chord either way; which spelling you meet depends on who wrote the chart.
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.
F9b5 has 2 of them, on strings 6-5-4-3-2 and the middle four strings, from the 5th fret up to the 6th — every inversion the chord has: A in the bass and Eb in the bass. The one to learn first is the A shape at the 5th fret, which is the easiest grip here.
Start with 1212x3 — 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 13th.
| Frets | Where | Bass | Top | Hand |
|---|---|---|---|---|
| 101001 | open position | F, root position | F | barred |
| 1212x3 | 1st fret | F, root position | G | all fretted |
| x23243 | 2nd fret | Cb, 2nd inversion | G | all fretted |
| x87887 | 7th fret | F, root position | Cb | barred |
| x-8-9-0-10-11 | 8th fret | F, root position | Eb | 1 open string |
| 13-12-13-0-0-13 | 12th fret | F, root position | F | barred |
| 13-12-13-12-12-13 | 12th fret | F, root position | F | barred |
The same notes rebuilt from scratch give 10 shell and 14 rootless voicings, each on its own page.
Tensions. A shell of F9b5, root, third and seventh, leaves a string free, and the tones that belong over it are the b13 (Db) and the 13 (D).
F9b5 is a dominant with its tension raised, so it still points at Bb — harder than a plain seventh does, because the altered tones sit a semitone from where they are going.
Voice by voice, F9b5 → Bb. 3 voices move by a semitone, and one note is common to both chords.
| In F9b5 | Moves | In Bb |
|---|---|---|
| F, the root | stays where it is | F, the fifth |
| A, the major third | rises a semitone | Bb, the root |
| Cb, the flat fifth | falls a semitone | Bb, the root |
| Eb, the flat seventh | falls a semitone | D, the major third |
| G, the ninth | falls a whole tone | F, the fifth |
Every note of F9b5 is in F whole tone and F lydian dominant.
Change one note of F9b5 and you have F7b5 (drop the ninth), F9 (the flat fifth becomes a fifth), Faug9 (the flat fifth becomes a sharp fifth) or F9#11 (add the fifth).
F9b5 is an altered chord — a dominant seventh with its fifth or ninth moved. Altered dominant chords on every root.
On F9b5’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.
Shows each chord the way this style would voice it, and marks which of its alternatives belong to the idiom.