Key Signatures and the Circle of Fifths

Most pieces stay mostly within one key, a home set of seven notes. Rather than marking every sharp or flat again and again, music collects them into a key signature at the start of every staff. Once you learn the pattern behind these signatures, the circle of fifths ties every key together into one tidy map.

What a key signature is

A key signature is the group of sharps (♯) or flats (♭) written just after the clef at the start of each line. Those accidentals apply to their note names for the whole piece, in every octave, so you do not have to write them again each time. If a signature has one sharp on the F line, then every F you meet is played as F♯ unless a temporary accidental says otherwise.

Each major key has a fixed number of sharps or flats. C major has none. Sharp keys add sharps one at a time, and flat keys add flats one at a time.

• Sharp keys: G (1), D (2), A (3), E (4), B (5), F♯ (6).
• Flat keys: F (1), B♭ (2), E♭ (3), A♭ (4), D♭ (5), G♭ (6).

The order of sharps and flats

Sharps always appear in the same order: F C G D A E B. Flats appear in exactly the reverse order: B E A D G C F. So a key with three sharps always has F♯, C♯ and G♯, and a key with three flats always has B♭, E♭ and A♭. The order never changes; only how many you use.

The circle of fifths

The circle of fifths arranges all these keys around a ring. Starting from C at the top, each step clockwise moves up a fifth and adds one sharp: C to G to D to A and so on. Each step counter-clockwise moves up a fourth and adds one flat: C to F to B♭ to E♭. The circle turns the counting above into a shape you can simply read off.

The inner ring shows each key's relative minor. A major key and its relative minor share the same key signature, so A minor sits inside C major (both have no sharps or flats), and E minor sits inside G major. Click around the interactive circle below: pick a key and watch the signature, the fifths, and the relative minor line up.

The circle is a memory aid you will use for years: it tells you a key's signature, its closest neighbours, and its relative minor, all from one position on the ring.