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Grade Three Music Theory - Lesson 4: Key Signatures

Key signatures have to be written very carefully. You need to make sure the flats and sharps are written

  • in the right order
  • in the right position

In the grade three music theory exam, you need to be able to write and understand key signatures with up to 4 sharps or 4 flats. 


Sharp Key Signatures

The sharps, in order, are F# - C# - G# - D#.

F# is used for G major and E minor
F# and C# are used for D major and B minor
F#, C# and G# are used for A major and F# minor
F#, C#, G# and D# are used for E major and C# minor


Position of the Sharps
In the treble clef, F# is always written on the top line:
position of f sharp treble clef

In the bass clef, it’s always written on the second line from the top:
position of f sharp bass clef


C# is written lower than the F#:
positions 2 sharps treble and bass


G# is written higher than C#:
positions 3 sharps treble and bass


D# is written lower than G#:
positions 4 sharps treble and bass

Look at the pattern: it goes down, up, down,  in both clefs!

 Flat Key Signatures

Position of the Flats
In the treble clef, Bb is written on the middle line:
positon b flat treble clef

In the bass clef, it’s written on the 2nd line from the bottom:
position b flat bass clef 


Eb is written higher than Bb:
positions 2 flats treble and bass 


Ab is written lower than Eb:
position 3 flats treble and bass


Db is written higher than Ab:
position 4 flats treble and bass


Look at the patterns: up, down, up, in both clefs - the opposite to the sharps' pattern!


 Relative Major and Relative Minor

We say that G major is the “relative major” to E minor, and that E minor is the “relative minor” to G major, because they use the same key signature.

To find out what the key signature is for a minor key, you first need to find the key signature for its relative major. So if you want to find the key signature for C# minor, you need to work out what the relative major of C# minor is.

To find a relative major, count upwards one tone and one semitone (make sure you count 3 different letter names too):
C# - D# is one tone,
D# - E is one semitone.
Therefore, the relative major of C# minor is E major. It has 4 sharps.


To find out the relative minor, do the opposite – count downwards one semitone and one tone:
G major
G- F is one tone,
F - E is one semitone.
So, the relative minor of G major is E minor.


 Key Signatures and Minor Keys

The key signature for a minor key includes all the sharp/flat notes from the natural minor scale – this is the same as the descending melodic scale.

For example, A minor melodic descending is A-G-F-E-D-C-B-A. There are no sharps and flats, so there are also no sharps or flats in the key signature for A minor.
Some students think that because A minor harmonic includes G#, there must be a G# in the key signature. This is a mistake.

When you write a minor scale with a key signature, you will need to add some accidentals (sharps and flats next to the notes) if the scale is:

  • harmonic minor, ascending or descending
  • melodic minor ascending only

Don’t forget that you also sometimes need to add naturals, to cancel flats from the key signature.

Here are some examples of minor scales with a key signature and accidentals:

All harmonic minor scales have a raised 7th note.


G minor harmonic (F becomes F#)
sharpened 7th note

C minor harmonic (Bb becomes B natural)
naturalised 7th note


All melodic minor ascending scales have raised 6th and 7th notes:

C# minor melodic (A and B become A# and B#)
sharpened 6th and 7th notes

F minor melodic (Db and Eb become D natural and E natural).
naturalised 6th and 7th notes


A quick way to check which key a key signature represents:

  • in sharp key signatures, the last sharp in the key signature is the leading note. It’s one semitone lower than the tonic of the major key. For example:
    last sharp is the leading note
    The last sharp is D#. The note one semitone higher than D# is E. This is the key signature for E major.

  • in flat keys, the last but one flat in the key signature is the tonic of the major key. For -example:
    last but one flat
    The last but one flat is Ab. This is the key signature for Ab major.


 For a complete list of all the major and minor scales, see our List of Musical Scales.