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.
F#m7b5 is F#, A, C and E — F#m7 with the fifth lowered a semitone.
It sounds hollow, and unmistakably going somewhere. Almost always the first chord of a minor ii–V–i, so it walks straight into an altered dominant.

| F# | A | C | E |
|---|---|---|---|
| 1 | ♭3 | ♭5 | ♭7 |
Pre-dominant — the ii of a minor key.
Also written F#ø, F#ø7, F#m7-5, F#m7(b5) or F# half diminished. 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.
F#m7b5 has 6 of them, on strings 6-5-4-3-2 and strings 6-5-4-3-2-1, from the 2nd fret up to the 5th — every inversion the chord has: F# in the bass, A in the bass and E in the bass. The one to learn first is the F# shape at the 2nd fret, which is the easiest grip here.
3 of them sit on strings 6-5-4-3-2, so you can run the inversions up one set without changing strings — which is the whole reason to learn them as a family rather than as separate grips.
Start with x-9-10-9-10-x — no barre. 1 of the 8 shapes here sits in open position. 4 of the 8 need a barre. Together they cover the neck from the 1st fret to the 14th.
| Frets | Where | Bass | Top | Hand |
|---|---|---|---|---|
| 202210 | open position | F#, root position | E | barred |
| 234252 | 2nd fret | F#, root position | F# | barred |
| xx4555 | 4th fret | F#, root position | A | barred |
| x97978 | 7th fret | F#, root position | C | all fretted |
| x-9-10-9-10-x | 9th fret | F#, root position | A | all fretted |
| x-x-10-11-10-12 | 10th fret | C, 2nd inversion | E | all fretted |
| 14-x-x-14-13-12 | 12th fret | F#, root position | E | all fretted |
| 14-x-14-14-13-x | 13th fret | F#, root position | C | barred |
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#m7b5, root, third and seventh, leaves a string free, and the tones that belong over it are the 11 (B) and the b13 (D).
F#m7b5 is the ii of E minor, which is where it is nearly always found: half-diminished, then an altered dominant, then the minor tonic.
In which keys. Every note of F#m7b5 belongs to E minor (the ii°, the supertonic) and G major (the vii°, the leading tone).
Every note of F#m7b5 is in F# blues, F# locrian, F# altered and F# half-whole diminished.
Change one note of F#m7b5 and you have F#dim (drop the flat seventh), F#dim7 (the flat seventh becomes a sixth), F#m7 (the flat fifth becomes a fifth), F#mMaj7b5 (the flat seventh becomes a major seventh) or F#7b5 (the minor third becomes a major third).
F#m7b5 is a diminished chord — root, minor third, flat fifth. Diminished and half-diminished chords on every root.
On F#m7b5’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.