The B Dominant 9th chord is a five-note chord made up of B, D♯, F♯, A, and C♯. It is built from a root, major third, perfect fifth, minor seventh, and major ninth.
Construction
B Dominant 9th = Root + Major 3rd + Perfect 5th + Minor 7th + Major 2nd = B · D♯ · F♯ · A · C♯
| Note | Interval | Degree |
|---|---|---|
| B | Root | 1 |
| D♯ | Major 3rd | 3 |
| F♯ | Perfect 5th | 5 |
| A | Minor 7th | ♭7 |
| C♯ | Major 2nd | 9 |
Key Signature
A dominant chord points home to the key a fifth below its root: the B Dominant 9th is the V (dominant) of E Major, so the relevant key signature is that key’s — 4 sharps (F♯, C♯, G♯, D♯). Spelled as a scale, these notes are B Mixolydian.
F♯C♯G♯D♯
Order of sharps
Sharps are added to a key signature in a fixed order. Each new sharp key adds the next sharp on the list.
F♯C♯G♯D♯A♯E♯B♯
Mnemonic: Father Charles Goes Down And Ends Battle
Chords in the Key of E Major
These are the triads built on each degree of the E major scale:
B Dominant 9th — Frequently Asked Questions
What is the B Dominant 9th chord on piano?
The B Dominant 9th chord contains the notes B – D♯ – F♯ – A – C♯. On piano, play these notes together to sound the chord.
What notes are in the B Dominant 9th chord?
The B Dominant 9th chord (B9) contains 5 notes: B, D#, F#, A, C#. Formula: R-M3-P5-m7-M9.
How is B9 used in music?
B9 is used in jazz, fusion, and contemporary music to add harmonic color. It appears as a dominant or tonic chord depending on context.
What is the scale degree formula for B9?
B9 uses scale degrees 1-3-5-b7-9, giving it its distinctive sound.