What is the circle of fifths?

The circle of fifths is a circular arrangement of the twelve keys where each key sits a perfect fifth from the next. Musicians use it to read key signatures, spot related keys, and plan harmonic movement — and with TwelveTones you can run the circle as a clickable practice session.

How the circle is built

Starting from C (no sharps or flats), the circle moves clockwise in fifths: C → G → D → A → E → B → F♯ → … Each step typically adds one sharp in major keys. Counter-clockwise, keys add flats (F, B♭, E♭, …).

The circle contains each of the twelve chromatic keys once. Enharmonic spellings (for example F♯ and G♭) name the same pitch with different notation conventions.

What is it good for?

• Memorising key signatures and closely related keys
• Planning cadences and modulations (the dominant is a fifth up)
• Running scales, chords, and licks systematically through keys

The circle of fourths — same structure, reverse direction

The circle of fourths is not a separate system. You walk the same circle backwards: in fourths instead of fifths. C → G → D becomes C → F → B♭ in reverse. Many players practise both directions because real music often modulates either way.

In the TwelveTones tool, 5ths follows the circle of fifths and 4ths follows the circle of fourths. The drill sticks when you play the live list: switch modes, check keys off, and keep session progress in the browser — that is what the homepage is for.