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Grade Three Music Theory - Lesson 4: Key Signatures

Key signatures are written after the clef and before the time signature. 

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 (whole step) and one semitone (half step). Make sure you count 3 different letter names too:
C# - D# is one tone (whole step),
D# - E is one semitone (half step).
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 minor 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: raise the 7th degree of the scale by one semitone (half step).
  • melodic minor ascending only (raise the 6th AND 7th degrees of the scale by one semitone (half step).

In some scales a raised note will be written with a sharp, in others you will need to add naturals, to cancel flats from the key signature.

Descending minor melodic scales should have no extra accidentals added.

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


All harmonic minor scales have a raised 7th degree of the scale. 

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

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


Don't forget that the degrees of the scale are worked out from the ascending scale, so in a descending scale the 7th degree will be at the beginning of the scale instead of the end.

For example, here is the descending scale of F minor harmonic. The 7th degree of the scale is E natural.



All melodic minor ascending scales have raised 6th and 7th degrees of the scale:

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



Here is 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 (note before the tonic). It’s one semitone (half step) 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 (half step) 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.

You need to remember that F major has only one flat (because there isn't a "last-but-one flat" in F major! 

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