The circle of fifths
You've no doubt heard this term before.
The circle of fifths provides us with an overview of all keys and how they correlate.
We formed the different keys by, for example, starting the C major scale at G and increasing the F to F sharp. C major and G major have 6 shared notes. So they are very similar.
This is why we say there is a relationship between the two keys.
To be precise, we say there is a fifth relationship. G is the fifth note in the C major scale (Latin: quintus = the fifth; see "Intervals" for more).
Let's now arrange the keys according to their relationship (related keys sit beside one another in the circle, so we get the circle of fifths:
In this diagram we can read the degrees of relationship very nicely. G major is related to C major and D major; A flat major to E flat major and D flat major, etc.
The further the keys are from one another, the less related they are to one another, and so the fewer notes they have in common. G major and A major only have 5 notes in common; G major and D flat major only have one common note.
F sharp major and G flat major are together at the end of the circle. But this is the same scale. The notes are written once with a sharp and once with a flat. We call this enharmonic change. So you can always write a key or a note in different ways. Example: For D flat you can also say C sharp. You cannot hear the difference; it is the same note. It is just shown differently on the music sheet.
If we do this in the F sharp major scale on every note, we get:
F sharp = G flat, G sharp = A flat, A sharp = B flat, B = C flat, C sharp = D flat, D sharp = E flat, E sharp = F
So exactly the G flat major scale.
