piano scale
G♭ major blues
Major pentatonic with a flattened third added next to the third — the two live side by side rather than replacing each other.
The same sounds spelled from the other side are F♯ major blues.
Written out
Every accidental is written in, rather than left to a key signature, so the letters can be read one at a time.
The step pattern
What is true of it
G♭ major blues is G♭, A♭, B♭♭, B♭, D♭ and E♭, and back to G♭.
Its steps are W – H – H – W+H – W – W+H, where W is a whole step and H a half.
Written correctly it needs 7 alterations, B♭♭ among them. That is what the letters force, and it is also why nobody writes music in this key: the same notes spelled from the other side are easier to read.
Chords made only of these notes
Found by testing every chord in the catalogue against these 6 sounds, not chosen.
Other scales on G♭
C maj bluesC♯ maj bluesD♭ maj bluesD maj bluesD♯ maj bluesE♭ maj bluesE maj bluesF maj bluesall 374