C#7#9 Dominant 7th
The C#7#9 chord is built from the notes C# – E# – G# – B – D##.
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Also known as
C##9C#7(#9)C#7(add#9)C#7add#9
Chord tones, one by one
C#Root
Root
The fundamental note the chord is built on — C#.
E#Third
Major third
Four semitones — makes the chord major (brighter, happier).
G#Fifth
Perfect fifth
Seven semitones — the most stable interval, reinforces the root.
BSeventh
Minor seventh (♭7)
Ten semitones — the dominant/minor seventh. Adds bluesy tension (7, m7).
D##Extension
Sharp ninth (♯9)
A ♯9 — the gritty 'Hendrix' tension over a dominant chord.
🎼 Related scales
🎹 Modal analysis
This chord implies the Half-whole diminished scale; its characteristic note is the ♭9 / ♭2.
🎸 Genres
Bebop jazz · Hard bop · Gypsy jazz
🎤 Artists who made it famous
Jimi Hendrix · The Beatles