The key of B major
B C♯ D♯ E F♯ G♯ A♯
5 sharps: F♯ C♯ G♯ D♯ A♯. Relative minor: The key of G♯ minor.
The triads of the key
I
B | ii
C♯m | iii
D♯m | IV
E | V
F♯ | vi
G♯m | vii°
A♯° |
The seventh chords
Imaj7
Bmaj7 | ii7
C♯m7 | iii7
D♯m7 | IVmaj7
Emaj7 | V7
F♯7 | vi7
G♯m7 | viiø7
A♯m7♭5 |
B major scale
Open it in the app: 6. Harmony, in B