Key signatures

Key idea The key signature is the group of sharps or flats at the start of every line. They apply to every note with that letter, in every octave, for the whole piece, unless an accidental says otherwise.

Instead of writing a sharp before every F in a G major piece, one sharp is placed on the F line at the start of each line. The key signature tells you the key at a glance.

The order of sharps and flats

Sharps always appear in the order F C G D A E B. Flats are the reverse: B E A D G C F.

Naming the key from the signature

• Sharp keys: take the last sharp and go up a half step. F♯ C♯ → a half step above C♯ is D major.
• Flat keys: the second-to-last flat names the key. B♭ E♭ A♭ → E♭ major.
• One flat (B♭) is F major, and no sharps or flats is C major. Just memorise these two.

The circle of fifths

Each step up a perfect fifth adds one sharp: C (0), G (1♯), D (2♯), A (3♯), E (4♯), B (5♯). Each step down a fifth adds one flat: F (1♭), B♭ (2♭), E♭ (3♭), A♭ (4♭).

• G major: F♯
• D major: F♯ C♯
• A major: F♯ C♯ G♯
• E major: F♯ C♯ G♯ D♯
• F major: B♭
• B♭ major: B♭ E♭
• E♭ major: B♭ E♭ A♭
• A♭ major: B♭ E♭ A♭ D♭