D♭ major blues

D♭1E♭2F♭♭3F3A♭5B♭6

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 C♯ major blues.

Written out

Fig. 2 · Db major blues, ascending

Every accidental is written in, rather than left to a key signature, so the letters can be read one at a time.

D♭WE♭HF♭HFW+HA♭WB♭W+HD♭

D♭ major blues is D♭, E♭, F♭, F, A♭ and B♭, and back to D♭.

Its steps are W – H – H – W+H – W – W+H, where W is a whole step and H a half.

Across the first twelve frets of the guitar its notes fall in 38 places, which is what makes a scale a shape rather than a list.

Found by testing every chord in the catalogue against these 6 sounds, not chosen.