Chord · F# Dominant 7♭9
F♯7♭9 Chord
F♯7♭9 is F#, A#, C#, E and G — spicy V chord; minor-key resolution.
F♯7♭9 on every instrument
The same 5 notes, 2 sets of hands. Open a diagram for alternate shapes, audio and the mistakes to avoid.
What F♯7♭9 is made of
F# Dominant 7♭9 (F# dominant 7♭9) is built from the notes F#, A#, C#, E, G, with the interval pattern 1, 3, 5, b7, b9. A common dominant 7♭9 chord across many styles.
Stack 1, 3, 5, b7 and b9 on a root of F♯ and you get F#, A#, C#, E and G. That interval recipe is what makes the chord a seventh flat nine chord — move the same shape to another root and the character travels with it, which is why C7♭9 sounds like a transposed F♯7♭9.
Dominant 7♭9: Spicy V chord; minor-key resolution.
Spelling: the notes above are written the way a score would write them, not simplified to the nearest piano key. That is why this chord is spelled with F♯ rather than its enharmonic equivalent.
Keys that contain F♯7♭9
No major or natural-minor key contains all 5 of these notes — this one gets borrowed.
Chords like this one sit outside the diatonic set — they arrive as secondary dominants, borrowed chords or passing harmony. Browse every key to see which progressions pull it in.
Other chords on F♯
Same root, different colour.
The same seventh flat nine shape, moved
The identical interval recipe, built on other roots.
Questions people ask about F#7b9
- What notes are in the F#7b9 chord?
- F#7b9 is made of F#, A#, C#, E and G — the 1, 3, 5, b7 and b9 degrees of a seventh flat nine chord built on F#.
- What keys use the F#7b9 chord?
- No major or natural-minor key contains all 5 notes of F#7b9. Chords like this arrive as borrowed harmony — secondary dominants, harmonic-minor colour, or chromatic passing chords — rather than as one of a key's native chords.
- How do you play F#7b9 on guitar and piano?
- This page shows F#7b9 on guitar and piano — 6 voicings in total. Each diagram links to the full instrument page with alternate shapes, audio and common mistakes.
- Is F#7b9 the same as Gb7b9?
- Yes. F#7b9 and Gb7b9 are enharmonic — identical pitches written two different ways. Which spelling you use depends on the key you are in; F#7b9 is the spelling this site treats as canonical.
Learn the theory behind it
Why F♯7♭9 behaves the way it does — the guides that explain the chord instead of just spelling it.