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 music Use 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 music Use 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 sharp2 sharps3 sharps4 sharps5 sharps6 sharps7 sharps
G majorD majorA majorE majorB majorF# majorC# major
E minorB minorF# minorC# minorG# minorD# minorA# minor
1 flat2 flats3 flats4 flats5 flats6 flats7 flats
F majorBb majorEb majorAb majorDb majorGb majorCb major
D minorG minorC minorF minorBb minorEb minorAb minor

how to work out key in music Use 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 usually 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 normally 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?


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?


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 music  Use 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 info  Played with an accent

important info  Repeated

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


It is C# minor.

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?


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!