The key of G♭ major
G♭ A♭ B♭ C♭ D♭ E♭ F
6 flats: B♭ E♭ A♭ D♭ G♭ C♭. Relative minor: The key of E♭ minor.
The triads of the key
I
G♭ | ii
A♭m | iii
B♭m | IV
C♭ | V
D♭ | vi
E♭m | vii°
F° |
The seventh chords
Imaj7
G♭maj7 | ii7
A♭m7 | iii7
B♭m7 | IVmaj7
C♭maj7 | V7
D♭7 | vi7
E♭m7 | viiø7
Fm7♭5 |
G♭ major scale
Open it in the app: 6. Harmony, in G♭