B13-alt7b9 Dominant 7th
The B13-alt7b9 chord is built from the notes B – D# – F# – A – C – C# – G#.
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Chord tones, one by one
Root
The fundamental note the chord is built on — B.
Major third
Four semitones — makes the chord major (brighter, happier).
Perfect fifth
Seven semitones — the most stable interval, reinforces the root.
Minor seventh (♭7)
Ten semitones — the dominant/minor seventh. Adds bluesy tension (7, m7).
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