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.
F7b5 is F, A, Cb and Eb — F7 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 | A | Cb | Eb |
|---|---|---|---|
| 1 | 3 | ♭5 | ♭7 |
Altered dominant — and the chord that makes the tritone substitution work.
Also written F7(b5), F7-5 or F7♭5. The same chord either way; which spelling you meet depends on who wrote the chart.
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.
F7b5 has 6 of them, on strings 6-4-3-2, the bottom four strings, strings 5-3-2-1, 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.
Start with xx3445 — no barre and low, at the 3rd fret. 1 of the 6 shapes here sits in open position. 1 of the 6 needs a barre. Together they cover the neck from the 1st fret to the 14th.
| Frets | Where | Bass | Top | Hand |
|---|---|---|---|---|
| 101201 | open position | F, root position | F | barred |
| xx3445 | 3rd fret | F, root position | A | all fretted |
| x67867 | 6th fret | Eb, 3rd inversion | Cb | all fretted |
| xx7867 | 6th fret | A, 1st inversion | Cb | all fretted |
| x-8-9-8-10-x | 8th fret | F, root position | A | all fretted |
| 13-x-13-14-12-x | 12th fret | F, root position | Cb | all fretted |
The same notes rebuilt from scratch give 14 drop 2, 9 drop 3 and 2 open string voicings, each on its own page.
Tensions. A shell of F7b5, root, third and seventh, leaves a string free, and the tones that belong over it are the b9 (Gb), the 9 (G), the #9 (G#), the b13 (Db) and the 13 (D).
F7b5 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, F7b5 → Bb. 3 voices move by a semitone, and one note is common to both chords.
| In F7b5 | 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 |
Every note of F7b5 is in F whole tone, F lydian dominant, F altered and F half-whole diminished.
Change one note of F7b5 and you have Fmaj7b5 (the flat seventh becomes a major seventh), Fm7b5 (the major third becomes a minor third), F7 (the flat fifth becomes a fifth), Faug7 (the flat fifth becomes a sharp fifth), F9b5 (add the ninth) or F/D# (the flat fifth becomes a fifth).
F7b5 is an altered chord — a dominant seventh with its fifth or ninth moved. Altered dominant chords on every root.
On F7b5’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.