F# Diminished 7th

Fretboard

On the fretboard, D# represents Eb.

Adjust labels, frets, and palette in the interactive view.

About

The F♯ fully diminished 7 (F♯–A–C–E♭) stacks four minor thirds, giving it a fully symmetrical structure. Each note can be respelled as a root — F♯°7 is enharmonically the same chord as A°7, C°7, and E♭°7 — meaning a single shape on the guitar can function as four different leading-tone chords depending on context. This flexibility makes dim7 especially useful as a passing or substitution chord, often resolving up a half step (here to G). All four tones carry the chord’s identity; the chord is defined by its symmetry, so removing any note weakens that quality. On guitar, one shape repeats identically every three frets. Compared to F♯m7♭5, dim7 is more unstable and dramatically tense.