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Victoria Williams

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Next UK ABRSM theory exams
Tuesday 6th November

How to Work out the Key of a Piece of Music

When you need to work out what key some music is in, there are some important rules to follow and some common traps avoid!

how to work out key in musicUse the key signature - this narrows the choice down to one major key  and one minor key

how to work out key in music

Find clues in the harmonic structure

how to work out key in music

Find clues in the notes which are emphasized

how NOT to work out key in music

Don't rely on accidentals

 


 

how to work out key in musicUse the Key Signature to Work out the Key 

Each key signature represents one major and one minor key.

0 flats/sharps
C major
A minor

 

1 sharp 2 sharps 3 sharps 4 sharps 5 sharps 6 sharps 7 sharps
G major D major A major E major B major  F# major C# major
E minor B minor F# minor C# minor G# minor D# minor A# minor

 

1 flat 2 flats 3 flats 4 flats 5 flats 6 flats 7 flats
 F major Bb major Eb major Ab major Db major Gb major Cb major
D minor G minor C minor F minor Bb minor Eb minor Ab minor

 

how to work out key in musicUse the Harmonic Structure to work out whether it's Major or Minor

Key is fixed by the use of the tonic and dominant chords. The tonic is chord I, and the dominant is chord V.

In C major, chord I is C-E-G. Chord V is made from the 5th note in the C major scale, which is G. Chord V is G-B-D.

Chords I and V in C major

In A minor, chord I is A-C-E and chord V is E-G#-B. (We raise the leading note to G#, as in the harmonic minor scale).

Chords I and V in A minor

important infoThe first full bar of the melody will use notes which belong to chords I and/or V. (You can also look at any upbeats, and at bar 2 as well, but bar 1 is the most important).

important infoThese notes will fall on the beat (not in between beats).

 

Here is an example.

What key is this in? There is one sharp. Is it G major or E minor?

G-major-or-E-minor

Chords I and V in G major are: G-B-D & D-F#-A

Chords I and V in E minor are: E-G-B & B-D#-F#

The time signature is 2/4, so the main beats are the notes which fall on the 1st and 2nd beats of the bar. These notes are boxed in red.

The notes in the boxes are G, D and G. 

The D natural shows us that it is G major. D natural does not occur in chord I or V in E minor.

 

Here is another example (in case you thought the lack of D# was enough to prove it is G major).

What key is this? There is one flat. Is it F major or D minor?

F-major-or-D-minor

Chords I and V in F major are F-A-C & C-E-G

Chords I and V in D minor are: D-F-A & A-C#-E

The time signature is 3/4, so we look at the notes on the 1st, 2nd and 3rd beats of the bar.

The notes on the beat are D, F, D and F.

D doesn't appear in chord I or V in F major. The key is D minor even though there are no accidentals!

 

how to work out key in musicUse the Emphasized Notes to Help You

There are many ways to emphasize a note. The tonic and dominant notes are often emphasized in these ways:

important info

Played on the first beat of the bar

important info

Played loudly

important infoPlayed with an accent

important info

Repeated

Look at this example. Is the key E major or C# minor?

tonic-dominant-emphasis

It is C# minor.

 

how NOT to work out key in music

Don't Rely on Accidentals

This is a very common error. Many people think that because there is an accidental in the harmonic minor scale, that there must also be accidentals in the minor key. This is not true:

important info

Melodies are built using the melodic minor scale. This has both sharpened and unsharpened notes. For example, A minor melodic contains the notes F natural, F sharp, G natural and G sharp.

important info

Only the 6th and 7th notes of the scale are affected. Some melodies don't use these notes.

important info

Accidentals can be added to a piece for decoration, without affecting the key.

 

Here is an example. 

What key is this in? There are no sharps or flats in the key signature. Is it C major or A minor?

C-major-or-A-minor

important info

 The notes which fall on the beat (starting from the upbeat) are G-C-E. They belong to chord I in C major.

important info The G# is just to decorate the melody. It does not affect the key of the piece. Listen to the extract for yourself!

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