The Circle of Fifths
The circle of fifths is a long-existing diagram used to examine scales side-by-side.
As we move from one point of the circle to the next, we will be listing scales a fifth up from the prior scale. Let’s start examining this concept by using the C major scale.
Below the C Major scale is a G Major scale. The notes are not exactly the same, but they are close.
The four became sharp. This will happen to each scale as we move a fifth up. Each scale will keep all previous accidentals, adding a new one in the process. The following diagram will illustrate this quite clearly. Review the diagram, but don’t worry about memorizing it. After listing these relationships, I’ll be introducing you to key signatures, which are much easier to memorize.
Also notice that E# and B# starts to show up. Yes, they DO exist. E# is essentially the same note as F, but it is written that way to give us a complete alphabet in the keys oc C# Major and F# Major.
At this point, we have all sharps.
To avoid double sharps, let’s rewrite our C# Major scale as D♭ Major. Notice that all notes are rewritten as their enharmonic equivalent.
We’ve now come full circle!
Thus we have our name, the circle of fifths. Why is this so important? Because we can now build key signatures.
Key signatures are the quickest way to remember and to derive intervals. Want to know if an interval is major? The key signature will tell you rather quickly, because you will be able to quickly recall all of the sharps and flats involved with any given major scale.
What is a key signature? These are used in standard notation, which is not covered in this book. That does not mean we cannot use them to our advantage, however. Think of the key signature as the unique traits a scale might leave behind. A key signature denotes their sharps and flats.
A C major key signature, for example, would be blank: no sharps, no flats. G major will have F#. D major will have F# as well as C#. Below, this is diagrammed:
If you memorize anything in music, it should be these signatures.
By knowing them well you will have the ability to improvise and compose easily. As a guitarist, thinking in key signatures will allow you to navigate the fretboard while keeping musical context in mind. As a composer, your intervals are only a moment away.
What about minor keys? Easy! Each key signature contains a Tritone. The tritone will resolve to two notes. These notes can be used to build two different chords. The I and the vi. The root of these chords can both be thought of as a tonal center for the given key signature. For example, A is the six of C. A minor shares the key signature of C major.
Notice, in the sharp key signatures, the last sharp happens to be the 7th scale degree. So, in order to quickly derive any key signature using sharps, you simply move a half step backwards, and that is your 7th scale degree. Then, starting on F, say your circle of fifths until you land on that note. So, in E Major, our 7th scale degree is D#. I then say my circle of fifths, starting on F. F, C, G and D. Those will be my sharps in that scale.
Notice that in the flat key signatures, the second to last flat is the root note. So, starting on B♭, recite your fourths until you land on your root note, then go one further. For example, in D♭, I would recite B, E, A, D, G, and C. Those would be my flats for that key.