Reference

Building Key Signatures

Major Scales

In order to build the key signature of a major scale or tonality, it is important to remember that the major scale of C does not have any key signature. On the contrary, any other scale may have sharps or flats.

All major scales based on a flat note, G flat, E flat, D flat, etc. use key signatures with flats. The only exception is F major. Therefore, when you are looking for a key signature, you can assume that it uses sharps if it is not F or does not begin with a flat note:

Once the accidentals used in the key signature are known, the following procedure may be used to build the key signature:

Building Key Signatures with Sharps:

Follow the order of the sharps until you reach the one that is a half-step below the major scale chosen. For instance, A major, F#, C#, G#. G# is a half-step below A. Therefore, sharps are F#, C#, G#.

Building Key Signatures with Flats:

Follow the order of the flats until you reach the one following the one that bears the same name in the major scale chosen. For instance, A flat major, B flat, E flat, A flat, D flat. D flat comes after A flat; therefore, flats are B flat, E flat, A flat, and D flat.

This method does not apply to the major scale of F that has a flat. Therefore, this key signature has to be memorized.

Building Key Signatures of Minor Scales

In the case of minor scales, the relative major has to be identified. Two relative scales have the same key signatures.

See S > Scales for related topics.

© 2011 J. Rodríguez Alvira

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13.11.05

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