Pattern of notes used to show key signatures and their relationships in a clock diagram.

The tones of the Chromatic Scale arranged so that each tone is a 5th above the previous tone. In this arrangement tones are harmonically consonant with their neighbors. When keys are arranged in fifths-order the similarity of adjacent scales becomes apparent. This is most easily illustrated with the Ionian Major scale. The C Ionian Major scale contains no flat or sharp tones. The key of G is a fifth above C. G Major has all the tones of the C Major scale except that F is raised a half-tone. Proceeding clockwise, we come to D. In the key of D both F and C are raised a half-tone. Since each key's neighbors are its closest relatives the Circle demonstrates the readiest harmonic movements. ( Wikipedia)

a circular visualisation of keys arranged clockwise to ascend by an interval of a perfect fifth

A clockface arrangement of the twelve pitches in the order of the number of accidentals in the key signature.

The arrangement in a closed circle of all 12 pitch names in such a way that, when proceeding clockwise along the circle any pair of adjacent pitches is a perfect fifth.

The succession of keys or chords proceeding by fifths.

In music theory, the circle of fifths (or cycle of fifths) is an imaginary geometrical space that depicts relationships among the 12 equal-tempered pitch classes comprising the familiar chromatic scale. The circle of fifths was first described by Johann David Heinichen, in his 1728 treatise Der Generalbass in der Composition.