F#-alt7#9 Half-Diminished
The F#-alt7#9 chord is built from the notes F# – A – C – E – G##.
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Also known as
F#altadd#15F#m7#9b5F#m7b5#9
Chord tones, one by one
F#Root
Root
The fundamental note the chord is built on — F#.
AThird
Minor third
Three semitones — makes the chord minor (darker, sadder).
CFifth
Diminished fifth (♭5)
Six semitones — a flat fifth. Creates instability, typical of m7♭5 and diminished chords.
ESeventh
Minor seventh (♭7)
Ten semitones — the dominant/minor seventh. Adds bluesy tension (7, m7).
G##Extension
Sharp ninth (♯9)
A ♯9 — the gritty 'Hendrix' tension over a dominant chord.
🎼 Related scales
🎹 Modal analysis
This chord implies the Locrian scale; its characteristic note is the unstable ♭5.
🎸 Genres
Modern jazz · Post-bop · Fusion