piano scale
A whole tone
A1B2C♯3D♯♯4E♯♯5F𝄪♯6
Six notes, every step a whole one. There are only two of these scales in all, and every note can be heard as the tonic.
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
AWBWC♯WD♯WE♯WF𝄪WA
What is true of it
A whole tone is A, B, C♯, D♯, E♯ and F𝄪, and back to A.
Its steps are W – W – W – W – W – W, where W is a whole step and H a half.
Written correctly it needs 5 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 6 sounds, not chosen.