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

In the grade three TRINITY music theory exam, you need to be able to write and understand key signatures with up to 2 sharps or 2 flats. 

(This doesn’t mean the Trinity exam is easier – the Trinity exam includes things that the ABRSM doesn’t. Compare the syllabuses here.)

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:

treble clef F# key signature


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

bass clef F# key signature

C# is written lower than the F#:

key signanture 2 sharps

G# is written higher than C#:

key signature 3 sharps

D# is written lower than G#:

key signatures 4 sharps

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:

key signature 1 flat


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

key signature 1 flat bass clef

Eb is written higher than Bb:

key signature 2 flats

Ab is written lower than Eb:

key signature 3 flats

Db is written higher than Ab:

key signature 4 flats

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#)

G minor harmonic


C minor harmonic (Bb becomes B natural)

C minor harmonic

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:

F minor harmonic descending

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

C# minor melodic ascending (A and B become A# and B#):

C# melodic minor ascending


F minor melodic ascending (Db and Eb become D natural and E natural):

F minor melodic ascending

Don’t forget that in the descending melodic minor scale, and the natural minor scale in both directions do not use any extra accidentals, when a key signature is used.

A minor melodic descending (or natural minor) (F and G natural):

A minor melodic descending

E minor melodic descending (or natural minor) (C and D natural):

E minor melodic descending

Tips

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

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.

Working out the Key

Often, you will want to know what key a piece of music is in, but because each key signature stands for two keys (one major, and one minor), you will need to do a little bit of detective work to figure out which key it is.

After checking the key signature, there are two more places to look to find clues about the key. You need to look at the harmony, and the melody.

Harmony

The word “harmony” means “chords”. If there are actual chords in the music, they will be a big help to you. But even if there are no chords (because the tune is just a single melody line, for example), you can look for patterns based on chords:

  • broken chords
  • arpeggios

You need to look out for the tonic triad of the key you think the music is in. We expect to find the tonic triads (or notes from the tonic triad):

  • right at the beginning of the piece (bar 1)
  • right at the end of the piece (last bar)
  • used more often than other chords

Melody

The word “melody” means the “tune”. The notes used in the melody will belong to the scale of the key the music is in. So, a piece in C major will use the notes from the C major scale, and a piece in A minor will use notes from the A minor scale.

You will remember though, that the natural minor and descending melodic minor scales use exactly the same notes as the major scale:

  • C major: C-D-E-F-G-A-B
  • A minor (natural/melodic descending): A-B-C-D-E-F-G

This means that if you see accidentals which belong to the ascending melodic minor scale (F# and G# in A minor), the music is probably in the minor key. But, if you see the notes without accidentals (F and G), it could be either key, and you will need to look for more clues.

As with the harmony, the tonic is the most important note in melody. You can expect to find the tonic note (also called “doh” or the “keynote”):

  • In bar 1
  • On a strong beat
  • Used a lot
  • Repeated, or accented
  • Used as the start/end note of a small section of a scale
  • Any combination of these

Here are some examples.

The key signature is used for D major and B minor – which key is it?

work out the key
  • The first bar is made up of the notes of a triad of B minor (B-D-F#).
  • The note B is on the strongest beat of bar 1, and is repeated in that bar.
  • There is a section of a scale leading down to B (F#-E-D-C#-B).

All of these clues lead us to the key of B minor for this piece.

The key signature is used for Bb major and G minor – which key is it?

work out the key
  • The note on the strongest beat of bar 1 is Bb.
  • Bb is the longest note at the start of the piece.
  • There are no Gs in the piece so far.
  • There is a section of a scale leading up from Bb (Bb-C-D-Eb).

The clues lead us to the key of Bb major.

The key signature is used for G major and E minor – which key is it?

work out the key
  • The note on the strongest beat of bar 1 is E.
  • There is a section of a scale leading down from E (E-D-C-B)
  • There is a D#, which is part of the E minor scale.

The clues lead us to the key of E minor.

Key Signatures Exercises

Hover your mouse over the questions (tap on mobiles) to reveal the answers.

Writing Key Signatures

Write out the following key signatures:

  1. D minor
    x
  2. E major*
    x
  3. B minor
    x
  4. Eb major*
    x
  5. Bb major
    x
  6. G minor
    x
  7. C# minor*
    x
  8. A major*
    x
  9. F minor*
    x
  10. E minor
    x

 

Relative Keys

Give the two keys (relative major and minor) which belong to each of these key signatures:

  1. *x
  2. x
  3. x
  4. *x
  5. *x
  6. x
  7. *
    x
  8. x
  9. x

Adding a Clef and Key Signature to Scales

Add the correct clef and key signature to make each of the scales named below. Add any accidentals (sharps or naturals) which are necessary.

 

  1. B harmonic minor
    scale-1
  2. C melodic minor*
    scale-2
  3. E major*
    scale-3
  4. F melodic minor*
    scale-4
  5. e) C# harmonic minor*
    scale-5
  6. f) E melodic minor
    scale-6
  7.  

Writing Scales with Key Signatures

Write as semibreves (whole notes) the scales named below:

  1. E major, descending, with key signature.*x
  2. F# harmonic minor, ascending, with key signature and any necessary accidentals.*x
  3. B melodic minor, ascending, with key signature and any necessary accidentals.x
  4. G harmonic minor descending, with key signature and any necessary accidentals.x