*It will be useful to look a diagram of the cycle while reading this section
The cycle of fifths is a multi purpose musical concept that can help develop your understanding of how music is written and analyzed. It is also referred to as “the cycle of keys” or “the cycle of fourths”. It will help to have a basic knowledge of music theory in order to utilize all the different aspects of the cycle but it is not absolutely necessary.
If you are familiar with the Roman Numeral System you may already know why it can be called the cycle of fifths or the cycle of fourths (refer to a diagram of the cycle). When moving clockwise around the cycle, the next note is always a fifth away from the previous one (C D E F G A B C D E F G A etc.…). When moving counter-clockwise around the cycle then the next note is always a fourth away from the previous letter (F G A Bb C D Eb F G Ab etc.…). (If you do not know what a fourth or fifth is, go to Table D and see the definition for an Interval).
Think of each letter in the cycle as representing more than just a note. Each letter can be the tonic of a key or the root of a chord/scale etc.
The first useful observation we will cover involves the I, IV and V chords of a key. The I, IV and V chords are the major chords of any key. They are always adjacent to one another in the cycle. For example C major is the I chord in the key of C. F major is the IV chord and G major is the V. If G major is the I chord then C major and D major are the IV and V respectively. If you are looking at a diagram of the cycle, the pattern the I, IV and V make within the cycle should be obvious. This makes the cycle an excellent tool for transposing or modulating to other keys.
Try doing the same with the relative minor chords as well. C major relative to A minor, F major relative to D minor and G major relative to E minor. Notice that A minor, D minor and E minor form the same pattern in the cycle. Now you can see how the I, II, III, IV, V and VI chords of any key fit into the cycle (the VII chord is part of the pattern as well). The same would hold true with altered versions of these chords. Being able to visualize this information is very useful when learning, composing and improvising music.
One of the most uniform cycle concepts has to do with keys and key signatures. You may want to divide the cycle into halves.
1) The “sharp” half is formed by moving clockwise around the cycle and adding one sharp to the next adjacent key starting with “C”.
2) The “flat” half is formed by moving counter-clockwise around the cycle and adding a flat to the next adjacent key starting with “C”.
Starting with the key of “C” there are no sharps or flats. Moving around clockwise to the key of “G” we find one sharp; F#. Moving around clockwise one more letter to the key of “D” we find there are two sharps; F# and C#. Onward to the key of “A” there are three sharps; F#, C# and G#. (Look at the cycle and notice that the sharps are being added as they appear in the cycle starting with F). This pattern continues until all the sharps are all used up.
The same pattern works for the flat keys starting with “F”. The key of “F” has one flat; Bb. Moving around counter-clockwise the key of “Bb” has two flats; Bb and Eb. The key of “Eb” has three flats; Bb, Eb and Ab. This pattern continues counter-clockwise around the cycle until all the flats are used up.
So one way to visualize the twelve keys is to relate them all to the key of “C” via the cycle of fifths. Each sharp key is formed cyclically by adding one new sharp from the cycle when moving in a clockwise fashion. Each flat key is formed from the key of “C” by adding one new flat from the cycle when moving in a counter-clockwise fashion.
There will be some examples of cycle based chord progressions in table F. When building chord progressions using the cycle it is a good idea to visualize the pattern you are creating. This will be especially useful if you want to transpose the chord progression. To better understand what I mean by visualize simply take one of the chord progressions in table F (or any chord progression for that matter) and look at how it fits into cycle.