C diminished scale.
A diminished scale, also known as the symmetric scale, is a scale in which the octave is divided symmetrically into eight intervals with the step pattern:
For example, the scale of C diminished is C D E♭F G♭A♭A B C.
Each diminished scale has four potential key-centers – the first, third, fifth, and seventh notes in the scale. This means that only three diminished scales are needed in order to cover all twelve keys. One starts from C, the second starts from C♯/D♭, and the third starts from D. The scale that starts from C contains the same notes as the E♯, G♯, and A scales. C♯ is the same as E, G, and B♭, and D is the same as F, A♭, and B (see diminished chord).
The diminished scale is like the augmented scale in its potential to occupy or suggest more than one key-center. Melodies and chords built on diminished scales are very unlike the familiar melodies built on diatonic harmony, and tend to have a disorienting effect on a key-center.