Key Signatures

C Major and A minor (in its natural form) scales contain no black notes. In order to build major and minor scales starting from any other note, it is necessary to alter one or more notes. For instance, in the scale of G major, note F is sharp. If you wished to write a melody in G major, you would need to alter all F notes. Key signatures are used to avoid writing so many accidentals.

Key signatures are placed at the beginning of each staff, between the clef and the time signature:

In the former melodic fragment, all Fs are sharp. Therefore, if you want to write a natural F, it should be preceded by a natural.  Scales with sharps in their key signatures are the following:

Scales with flats in their key signatures are the following:

These accidentals, written between the clef and the time signature affect all of the notes of that name throughout the piece, including those in other octaves.

 

 

The first letter of each word in the following sentences tells us the order that the flats and sharps are entered in a key signature:

 

 

A key signature that uses all seven possible flats will look like this:

A key signature that uses all seven possible sharps will look like this:

In key signatures that contain sharps, to identify the key signature look at the last sharp. The key note will be one diatonic (following the scale) semitone higher. I.e. the next letter name up the scale. The last sharp indicated above is the B#. Therefore, moving up one step, this key signature belongs to C#-major.

 

In key signatures that contain flats, to identify the key signature look at the second from last accidental. This is the key note. In this example the second from last flat is Cb. Therefore, this key signature belongs to C-flat major. N.B. F Major has only one flat and so cannot be worked out in this way. This one must just be remembered as must C Major.