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 B♭ 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 8 alterations, C𝄪 and G𝄪 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