Key signatures and the circle of fifths

Key signature

The sharps or flats at the start of each staff form the key signature. They apply to the whole piece.

Order of sharps and flats

• Sharps: F C G D A E B
• Flats: B E A D G C F (the reverse)

Reading a key

• For sharps: the last sharp is the leading tone, so the key is a semitone higher. Two sharps (F♯, C♯) means D major.
• For flats: the second-to-last flat names the key. Two flats (B♭, E♭) means B♭ major. One flat is F major.

The circle of fifths

Arrange keys so each step clockwise goes up a perfect fifth: C → G → D → A → E → B → ...

Each step clockwise adds one sharp. Counter-clockwise adds one flat (C → F → B♭ → E♭ ...). Neighbouring keys differ by one accidental.

Relative minor

Every major key shares its signature with a minor key. A minor goes with C major, E minor with G major, D minor with F major.