So what you're saying is keys go around in circles and leave their signature somewhere from time to time?
In this tutorial, we'll be taking a look at how different scales can be obtained by using the circle of 5ths. We'll also understand how key signatures affect the song. So, let's have some fun.
The circle of fifths is an actual diagram in the form of a circle, that helps us in forming major scales and their relative minor counterparts. The circle itself looks something like this:
In the image above we have all possible major scales that can be formed. Everything starts at the top with the C major scale.
So why is it called the circle of 5ths? Because the difference between each root note of the major scales is a fifth. Let's understand what this means.
If you look at the top of the diagram, as we've seen, we have the C major scale. If we go through the circle clockwise, the first major scale we encounter is the G major scale. The tone difference between C and G is a rising fifth. Next in line is the D major scale. The difference between G and D is once again a rising fifth and so on.
We can go through the circle counter clockwise, the first major scale we encounter is the F major scale. The difference between C and F is of course a falling fifth. And so on.
One thing you may notice is that at some point these scales overlap, meaning that you have two different names for scales that seem to be one and the same. Which, enharmonically speaking, they are, because they have the same pitches, but with different names. From my experience, you will most likely never encounter the C♭ key (everyone will use B) or the C♯ key (everyone will use D♭). G♭ and F♯ may be used, but in the end it all boils down to preference (I usually use F♯).
Another thing to notice is that next to each scale we have a staff with a bunch of sharps or flats on it (aside from the C major scale). That, my fellow music enthusiasts, is the key signature.
A key signature refers to the sharp notes or flat notes a certain scale (or key) has. As we can see from the circle of 5ths, aside from the C major scale (and as a result A minor), every other scale has at least one accidental in their signature.
So why are key signatures important? Because when a song is written in a key that has an accidental in its signature (for example, G major), whenever you encounter the note or notes that have accidentals in the key signature (in the case of G major, it has an F♯ in its signature), then you are obligated to play those notes with the accidentals applied, unless stated otherwise, usually by the use of a natural accidental (in the case of G major, we will always play the F notes on the staff as F♯).
Key signatures therefore allow musicians to avoid placing an accidental each and every time a note should have one because of the scale it is part of. Placement wise, a key signature is located at the very beginning of a song or anywhere else a key change is required in more complex pieces of music.
That about covers it for this tutorial. And since we already know how to read sheet music properly and how to play single notes from a scale, it's time to go further beyond and learn about triads and chords, starting from the next tutorial. See you then.