F Phrygian dominant

F1G♭♭2A3B♭4C5D♭♭6E♭♭7

The fifth mode of harmonic minor: a flat second over a major third, so the step from the second to the third is a step and a half.

Written out

Fig. 2 · F Phrygian dominant, ascending

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

FHG♭W+HAHB♭WCHD♭WE♭WF

F Phrygian dominant is F, G♭, A, B♭, C, D♭ and E♭, and back to F.

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

On the same tonic, F Phrygian differs from it by exactly one note.

Across the first twelve frets of the ukulele its notes fall in 30 places, which is what makes a scale a shape rather than a list.

Found by testing every chord in the catalogue against these 7 sounds, not chosen.