C diminished (half–whole)

C1D♭♭2E♭♭3E3F♯♯4G5A6B♭♭7

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.

Written out

Fig. 2 · C diminished (half–whole), ascending

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

CHD♭WE♭HEWF♯HGWAHB♭WC

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.

Found by testing every chord in the catalogue against these 8 sounds, not chosen.