circle of fifths
theorySIR-kul of fifths
A diagram arranging all twelve keys by ascending perfect fifths, showing the relationships between keys and their key signatures
The circle of fifths places C at the top (no sharps or flats) and moves clockwise through keys adding one sharp each step (G, D, A, E, B, F♯) and anticlockwise adding one flat each step (F, B♭, E♭, A♭, D♭, G♭). The bottom of the circle is the enharmonic meeting point where F♯ and G♭ are the same key. Adjacent keys on the circle are closely related and share the most common chords. The circle is the single most useful diagram in tonal theory.
The circle of fifths was first described by the Ukrainian composer and theorist Nikolay Diletsky in his 1679 treatise on composition.