Work out the key of a piece of music – flats

How to work out the key of a piece of music using flats

In music theory exams you may be asked to work out a key from a piece of music with accidentals. In this example, I am going to use flats.

Question: What is the key of the following piece of music?

When the key is a major key

Step 1:

Make a list of all the flats which appear in the example above (Some are duplicated so there is no need to write those):

E flat;    B flat;   A flat;

Step 2:

Put the flats in the order they would appear in a key signature.  I use the phrase Bad Elephants Always Drink Good Coffee First

B flat (Bad);   E flat (Elephants);   A flat (Always)

Step 3:

We have now discovered there are 3 flats.  Look at the last flat, A flat, and then move back to the flat before the last one, the penultimate flat, E flat.    This means that E flat major is the major key of the example above.

When the key is a minor key

Step 1:

Write down the order of flats as they appear in the example above.  There is no need to write down any flats which are duplicated

E flat;  A flat

Step 2:

Write down the flats in the order they would appear in a key signature. I use the phrase Bad Elephants Always Drink Good Coffee First.

E flat and A flat are already in the correct order but B flat is missing!  Check to see if there are any B’s in the example.  We can see there are 2 B’s but both of them are B natural and not B flat.  We know that flats always appear in a key signature in the same order – you cannot miss any out!  If this was a major key, there would HAVE To be a B flat in front of E flat and A flat.  Immediately this should alert you to the idea that the example may be in a minor key rather than a major key.

Step 3:

Work out the relative minor of E flat major, which has 3 flats, B flat, E flat and A flat.  The 6th note of E flat major is C so C minor is the relative minor.  Working out the notes of C harmonic minor we have:  C  D  Eb  F  G  Ab  B  C

The 7th, leading note, of C harmonic minor is B natural.

Step 4:

We can now see that in the example above, the key must be C minor and not E flat major

Note:

When working out whether a key is major or minor, the biggest clue is the 7th or leading note of the minor key, which is always raised by one semitone in the harmonic minor form.  

 

 

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