C#mi(maj13b5b9) Diminished
The C#mi(maj13b5b9) chord is built from the notes C# – E – G – B# – D – D# – A#.
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Also known as
Chord tones, one by one
Root
The fundamental note the chord is built on — C#.
Minor third
Three semitones — makes the chord minor (darker, sadder).
Diminished fifth (♭5)
Six semitones — a flat fifth. Creates instability, typical of m7♭5 and diminished chords.
Major seventh
Eleven semitones — a lush, jazzy seventh just below the octave (maj7).
Flat ninth (♭9)
A ♭9 — sharp, dissonant tension typical of altered dominant chords.
Ninth (9)
A 9th — colorful extension a whole step above the octave.
Thirteenth (13)
A 13th — full, rich top extension.
🎹 Modal analysis
This chord is so rich it doesn't fit a single scale: it's a polychord (an “upper structure”) that stacks tensions from several scales at once. It doesn't work like a dominant that “wants” to resolve — it's pure color: picture one triad floating over an unrelated bass, the kind of sound used in reharmonization and modal passages. To make sense of it, follow the note-by-note breakdown above.
🎸 Genres
Modern jazz · Fusion · Film & TV scoring · Impressionism