The circle of fifths

Put the 12 keys in a circle and the relationships between them become visible. It is the best map of keys there is.

Building the circle

Arrange the 12 keys like a clock, with C at the top. Going clockwise, each key is a perfect 5th above the previous one: C G D A E B, F♯/G♭, D♭ A♭ E♭ B♭ F, and back to C. Going counter-clockwise, each step is a perfect 4th above, which is a 5th below. Read that way it is sometimes called the circle of fourths; it is the same circle.

Sharps and flats

Each step clockwise adds one sharp, or removes one flat. Each step counter-clockwise adds one flat, or removes one sharp. At the bottom the circle meets itself through enharmonic keys: F♯ = G♭. B/C♭ and C♯/D♭ are also enharmonic, but most circles show only B and D♭.

Neighbouring keys

Neighbouring keys differ by one note. C and G share everything except F / F♯. That is why music moves easily to neighbouring keys (Module 14). For any key on the circle, its neighbour counter-clockwise is its IV, the subdominant, and its neighbour clockwise is its V, the dominant. The three together hold the three major chords of the key (Module 8).

The inner ring of most circles shows the relative minor keys (Module 6). For now, note that each one shares its key signature with the major key next to it.