B9 — B, D♯, F♯, A, C♯ — is a dominant 9th chord: major triad + minor 7th + major 9th — a dominant chord with the 9th added on top for a rich, slightly bluesy colour.
Intervals
The B dominant 9 chord stacks two thirds on the root. Each interval and its size in semitones:
- B→D#major 3rd4 semitones
- D#→F#minor 3rd3 semitones
- F#→Aminor 3rd3 semitones
- A→C#major 3rd4 semitones
On the keyboard
Each note of the B dominant 9 chord highlighted on a piano. Pitch class is what matters — any octave works.
On the guitar
One voicing of the B dominant 9 chord on a six-string guitar fretboard.
- 1B
- 3D#
- 5F#
- ♭7A
- 9C#
Common mistakes
The defining note is the 9th (C♯). It sits more than an octave above the root, which is why the chord needs a wide voicing — in tight piano voicings the 9th usually appears in the top register while the root and lower triad tones cluster below.
In context
Functions as the V9 in its target key — a richer, more colourful alternative to the plain V7 dominant.
Drill it
The B dominant 9 chord is one of 48 in the Chord Trainer. Open the full trainer to practice it alongside related chords with timing and best-time tracking.
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Frequently asked
- What notes are in a B9 chord?
- B9 contains five notes: B, D♯, F♯, A, C♯.
- How is B9 different from B7?
- B9 adds the 9th (C♯) on top of the underlying 7th chord. The 9th extends the chord into the next octave and adds harmonic colour.
- When is B9 used in music?
- Functions as the V9 in its target key — a richer, more colourful alternative to the plain V7 dominant.