The B Dominant 7th chord is a four-note chord made up of B, D♯, F♯, and A. It is built from a root, major third, perfect fifth, and minor seventh.
Construction
| Note | Interval | Degree |
|---|---|---|
| B | Root | 1 |
| D♯ | Major 3rd | 3 |
| F♯ | Perfect 5th | 5 |
| A | Minor 7th | ♭7 |
B Dominant 7th Inversions
| Position | Notes |
|---|---|
| Root Position | B – D♯ – F♯ – A |
| 1st Inversion | D♯ – F♯ – A – B |
| 2nd Inversion | F♯ – A – B – D♯ |
| 3rd Inversion | A – B – D♯ – F♯ |
Key Signature
A dominant chord points home to the key a fifth below its root: the B Dominant 7th 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.
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.
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Chords in the Key of E Major
These are the triads built on each degree of the E major scale:
How B Dominant 7th functions in a key
The same chord takes on a different harmonic role depending on the key it appears in. Here is where B Dominant 7th sits diatonically across the common keys:
- In E major, B Dominant 7th is the V chord — the dominant.
- In C♯ minor, B Dominant 7th is the ♭VII chord — a mediant / color chord.