piano scale
A♭ double harmonic
Two augmented seconds in one scale, one above the tonic and one below the octave.
The same sounds spelled from the other side are G♯ double harmonic.
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
A♭ double harmonic is A♭, B♭♭, C, D♭, E♭, F♭ and G, and back to A♭.
Its steps are H – W+H – H – W – H – W+H – H, where W is a whole step and H a half.
Written correctly it needs 6 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.
On the same tonic, A♭ harmonic major differs from it by exactly one note.
Chords made only of these notes
Found by testing every chord in the catalogue against these 7 sounds, not chosen.
Other scales on A♭
C dbl harmC♯ dbl harmD♭ dbl harmD dbl harmD♯ dbl harmE♭ dbl harmE dbl harmF dbl harmall 374