Melody - Key Signatures

A key signature is a group of accidentals placed at the beginning of every line of music, just to the right of the clef, that instructs the performer to apply the accidentals to every corresponding note in the piece, no matter the octave, unless otherwise specified. Key signatures can only either be sharps or flat, never both. They it unnecessary to put a sharp or flat before every sharped or flatten note in the piece.

For example, this key signature indicates every F# in the piece should be sharped, regardless of the octave.

In C major, there are no sharps or flats so the key signature has no sharps and no flats.

C Major Scale

C Major Key Signature

In G Major, there is one sharp (F#). So the key signature is F#.

G Major Scale

G Major Key Signature

In F Major, there is one flat (B♭). So the key signature is B♭.

Purposes of a key signature:

• It indicates the key of the piece.
• It reduces the need for including sharps, flats and naturals with every note.

To work out the key of a piece of music:

• Look at the signature.
• Look at the last note - often (but not always) this will be the key note.