Key signature
A key signature is the group of sharps or flats written after the clef at the start of every staff, telling you which notes are raised or lowered throughout the piece.
What does a key signature tell you?
A sharp on the F line means every F is played as F♯: in every octave, in every bar, until the signature changes. That saves writing the same sharp on every F of the piece.
Sharps and flats always appear in a fixed order:
- Sharps: F♯, C♯, G♯, D♯, A♯, E♯, B♯
- Flats: B♭, E♭, A♭, D♭, G♭, C♭, F♭
So a signature of two sharps is always F♯ and C♯, never any other pair.
How do you read the key from it?
- Sharps: take the last sharp and go up one semitone. Last sharp C♯ gives D major.
- Flats: the second-to-last flat is the major key. B♭ and E♭ give B♭ major. A single flat is the exception to learn on its own: F major.
- No sharps or flats: C major.
- Then the minor: each signature also belongs to the relative minor, three semitones below. One sharp is G major or E minor; two flats are B♭ major or G minor.
What is the most common confusion?
Expecting the signature to say major or minor. It cannot: G major and E minor share it exactly. To decide, look at which note the music comes home to, and for a raised seventh (D♯ in E minor) appearing as an accidental.
The other is mixing it up with an accidental, a sharp, flat or natural written beside one note. An accidental lasts only until the end of its bar. The key signature lasts the whole piece.
Try it: the circle of fifths lesson explains why the order never changes and ends with a drill that shows you a signature and asks for the key.