piano scale
A♭ whole tone
A♭1B♭2C3D♯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.
The same sounds spelled from the other side are G♯ whole tone.
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
A♭WB♭WCWDWEWF♯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.
Chords made only of these notes
Found by testing every chord in the catalogue against these 6 sounds, not chosen.