F#dim7 Chord on Guitar
F#dim7 = F# – A – C – D# (Root, Minor 3rd, Tritone, Major 6th)
F#dim7 stacks a third minor third on top of the F#dim triad, adding the diminished seventh, and in doing so becomes something genuinely unusual in tonal harmony: a chord built entirely out of equal minor-third intervals, which makes it perfectly symmetrical and, on a fretted instrument, movable in a way no other common chord quality is.
F#-A-C-D#: four notes, each a minor third above the last, closing the loop back to F# an octave up after four such steps. Because the interval pattern repeats every three semitones, there are only three genuinely distinct diminished-seventh chords on the entire guitar neck — F#dim7, Gdim7, and G#dim7 already exhaust the possibilities, since Adim7 four frets up shares every pitch with F#dim7. That symmetry makes dim7 chords the guitarist's most flexible chromatic tool: the same fingering, moved in minor-third jumps, produces the identical chord, which is exploited constantly for chromatic passing motion and modulation between distantly related keys.
Fingerings
Barre (2nd fret)
How to Practice It
Once this shape is learned, practice sliding it up three frets at a time and notice that the notes don't actually change — that's the clearest way to internalize the symmetry rather than just being told about it. Use F#dim7 as a passing chord between two diatonic chords a step apart, since that chromatic connective function is how the chord earns its keep far more often than as a chord that's simply named and played in isolation.
Common Progressions
- G – F#dim7 – G/B (I sliding chromatically through a passing dim7 to a first-inversion I)
- Gm7 – F#dim7 – Fmaj7 (a jazz chromatic descent using the symmetrical chord as connective tissue)
- D7 – F#dim7 – G (V7 substituting into a diminished passing chord before resolving to I)
- F#dim7 – G – Em – C (a leading-tone resolution opening a longer progression in G major)
FAQ
- Why are there only three unique diminished-seventh chords on guitar?
- A dim7 chord is built entirely from stacked minor thirds (three semitones each), and three semitones divides evenly into the twelve semitones of an octave four times, so any dim7 shape repeats its exact pitch set every three frets — meaning only three starting positions produce genuinely different note collections.
- What's the difference between F#dim and F#dim7?
- F#dim7 adds a fourth note, the diminished seventh (D#), on top of the triad's root, minor third, and diminished fifth, extending the same stacked-minor-thirds pattern one step further and making the whole chord symmetrical.
- How is F#dim7 used in practice?
- Almost always as a chromatic passing or connecting chord — sliding between two diatonic chords, substituting briefly for a dominant seventh, or bridging a modulation to a distantly related key — rather than as a chord a progression settles on.
- Is F#dim7 hard to play?
- It's a compact, low-position barre with a fairly small stretch, so it's not physically demanding; the real challenge is recognizing where and why to use it, since its symmetry makes it flexible but also easy to place awkwardly if the ear isn't guiding the choice.
- Can F#dim7 be renamed and thought of as a different chord entirely?
- Yes — because of its symmetry, the identical four notes can be spelled and functionally understood as Adim7, Cdim7, or D#(Ebdim7) depending on which note is treated as the root, and jazz players routinely reinterpret it this way to justify unexpected resolutions.
F#dim7 on other instruments: F#dim7 on Piano. Related: how chords are built, chord finder.