What is a Key?
The Key of a piece of music refers to the scale that the notes used to make up a tune are from. For example, if we look at the tune below, we see that the B in the tune is flattened, which shows that it is using the scale of F major.
Major and Minor are the two most common scales used in western music. There are actually lots of different scales, however most music is written in either a major or minor key.
Major keys are often described as being “happier” in feel, whilst the minor keys are usually referred to as “sadder”.
All minor keys are related to a major key and use the same sharps or flats, so whenever we see a key signature, it shows us that the piece is in one of two related keys.
How are they related?
To find out which major key a minor scale is related to, you simply go up by 4 semitones. For example, in the case of A minor we go up 4 semitones (A-A#-B-C) and find that it is related to the scale of C major (no sharps or flats). So, if we play the notes of a C major scale, but start and finish on A, we are playing a pure A minor scale.
Unfortunately things aren’t quite that straightforward as there are different types of minor scale. The most common type of Minor is a Harmonic Minor, and this is all we will be talking about here. For this we play the pure minor we have just worked out, but we also sharpen the 7th note so our A minor scale becomes this:
The reason that the 7th note is sharpened is quite complicated, so we won’t go into it here, but if you want to find out more see this article.
The sharpened 7th note does not go in the key signature of a piece, instead it is placed in the music. Thus, as we said earlier, each key signature could be one of two keys. For example, an F# and C# could be D major or it could be B minor. If it is B minor we would expect to see lots of A sharps (the seventh note of a B minor scale).