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