piano scale
C♯ diminished (half–whole)
The same eight notes started a half step earlier: the scale that spells a dominant seventh with a flat ninth and a sharp ninth at once.
The same sounds spelled from the other side are D♭ diminished (half–whole).
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
C♯ diminished (half–whole) is C♯, D, E, E♯, F𝄪, G♯, A♯ and B, and back to C♯.
Its steps are H – W – H – W – H – W – H – W, where W is a whole step and H a half.
Written correctly it needs 6 alterations, F𝄪 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.
Chords made only of these notes
Found by testing every chord in the catalogue against these 8 sounds, not chosen.
Other scales on C♯
C dim H-WD dim H-WD♯ dim H-WE♭ dim H-WE dim H-WF dim H-WF♯ dim H-WG♭ dim H-Wall 374