The 12 keys
So what is a key?
C major for example. If you move (freely) in the C major scale, you could say that the key is C major.
Let's take another closer look at the C major scale:
If we look closer we can see the scale has a symmetrical setup. The first 4 notes have the following relationship with one another:
whole tone - whole tone - half tone
There is the same relationship with the second 4 notes.
We call these four tone series tetrachords (from the Greek, tetra = four). Both tetrachords have a whole tone between one another.
Now we'll begin the scale from the fifth note, the G and at the same time the first note of the second tetrachord, and continue the white notes scale. This then looks as follows:
In future I will dispense with identifying the whole tone steps. Only the half tone steps will therefore be marked.
So now let's take a look at the half tone steps with our new scale. The first tetrachord has the right setup: whole tone - whole tone - half tone.
With the second tetrachord, however, the setup that we need for a major scale is no longer right. To restore the half tone between the 7th and 8th notes, we increase the F by a half tone to F sharp.
The half tones are now sitting at the right places, and we see the G major scale in front of us.
We can continue this sequence any way we want. We take the second 4 notes of the G major scale again. Now we need to increase the C to C sharp and consequently get our D major scale.
And so on and so on ...
Here is an overview:
With every new key formed we get another sharp.
C major has no accidentals. G major has a sharp (an F sharp); D major already has two sharps (F sharp and C sharp), etc.
We should note here, however, that the accidentals are always listed in this sequence:
F sharp - C sharp - G sharp - D sharp - A sharp - E sharp
Use this overview to make it once again clear to yourself that the last 4 notes of a key are always the first 4 notes of the next key (sometimes the notes are written an octave lower).
In the overview we were talking about 12 keys, but we can only see 7 keys in it! Of course we could continue our system and would also actually get 12 different keys. The next key would be C sharp major (additional accidental: His), followed by G sharp major (additional accidental: F double sharp), etc.
We get scales in which every note has an accidental; some even have double accidentals. This then actually gets pretty demanding and complicated.
But as we have already learnt, we can call C sharp D flat, and also set up the scale from this note in exactly the same way. As a side note: the interchanging of note names is called enharmonic change.
Let's begin with C major again.
As the scale is symmetrical, we can consider the first 4 notes just as well as we can the end of the scale. If we continue the scale down with the white notes scale, we get:
This time the half tone step between the 7th and 8th notes is right. But as we immediately see, the second half tone step is between the 4th and 5th notes. We can correct this by reducing the B to Bb. The setup is then right again and we get the F major scale.
As before with the sharp keys, we also form further keys here.
Here is the overview of the b keys:
With every new key we get an additional b.
The accidentals are also listed in sequence here.
B flat - E flat - A flat - D flat - G flat - C flat
Similar to the sharp keys, the first 4 notes are the same as the second 4 notes of the following key.
We could also form further keys here as well, but there would be nothing new. G flat major can also be written as F sharp major. Instead of writing the next key with 7 ♭s, we generally prefer to choose the notation with 5 sharps.
But 6 accidentals are more than enough, don't you think?
Done!!!
That was a very long section. To get really fit with the keys, you really should do the corresponding exercises.
Enjoy!
