guitar scale
G♭ blues
Minor pentatonic with one note squeezed in between the fourth and the fifth. It is written as a flattened fifth, so the fifth letter carries both of them and the fourth keeps its own.
The same sounds spelled from the other side are F♯ 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♭ blues is G♭, B♭♭, C♭, D♭♭, D♭ and F♭, and back to G♭.
Its steps are W+H – W – H – H – W+H – W, where W is a whole step and H a half.
Written correctly it needs 8 alterations, B♭♭ and D♭♭ 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.
Across the first twelve frets of the guitar its notes fall in 40 places, which is what makes a scale a shape rather than a list.
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 bluesC♯ bluesD♭ bluesD bluesD♯ bluesE♭ bluesE bluesF bluesall 374