Circle Of Fifths

The Circle of Fifths (or Cycle of Fifths) is a theoretical concept commonly used as a compositional tool for quickly developing nice-sounding chord progressions. There are many ways to illustrate it, but a very useful version includes three concentric rings occupied by a total of 36 chord symbols. In this diagram, note how seven small “pieces of the pie”, each distinguished by a different color, comprise a section of the pie:

Those pieces of different colors identify seven chords comprising a chord family produced by a basic harmonization of the C Major scale, as explained in the previous section on Chord Progressions. Any of those seven chords are useful in a chord progression in either the key of C or its relative minor key A Minor. Consider the outline of the colored section (roughly the size of a quarter of the pie) to be a chord family “template” that can be visually rotated to any of 12 positions depending on which key you want for your chord progression. We’ll visualize the movement of the template while the chord symbols throughout the circle remain fixed in their current positions.

Looking closely at the diagram, you’ll see two Roman numerals in each of the seven colored pieces. One is the chord number in a chord progression in a major key, and the other is the chord number in a chord progression in the relative minor key. We see C, F and G chords as the I-IV-V in the key of C, and we see Am, Dm and Em as i-iv-v chords in the key of Am. (The innermost ring of the circle includes only diminished chords, which are relatively difficult to use at our level of study, so we can ignore those for now.)

You must visualize those chord numbers as being attached to the template when you rotate it to select the key (while all the chord symbols remain fixed in their “background” positions). For example, visualize the rotation of the template one notch in the clockwise direction. Now we see the chords G, C and D shown as the I-IV-V in the key of G, and we see Em, Am and Bm as the i-iv-v chords in the key of Em.

Many resources on the internet explain the Circle of Fifths, but there is no definitive standard description, unfortunately. All of them have the same outer ring with 12 parts labeled C, G, D, A, E, etc., but there can be minor differences. For example, the picture above shows the bottommost section of the outer ring as F♯, but others show that section as either the enharmonic equivalent G♭ or both (“ F♯/ G♭”).

A very useful explanation of the Circle of Fifths is at https://markhahnguitar.wordpress.com/2018/03/18/decoding-music-using-the-circle-of-fifths/.