The Circle of Fifths is a concept used in music theory that shows the relationship between all of the musical keys. The circle is also used to show the number of sharps and flats in a particular key, which is helpful to understand the relationships between major and minor keys as well. Finally, the concept gets its name because the Circle of Fifths is presented as a circle of musical keys, these are all separated by degrees of a fifth.
The Circle of Fifths usually looks like this:Circle of fifths deluxe 4 by Just plain Bill [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0/)]
The key of C is at the top of the graph because the key of C has zero sharps or flats. The key of G which is located one notch to the right of the C has 1 sharp. We know it has 1 sharp because it is 1 notch to the right of C. The keys on the right side show us the number of sharps in that key. The keys on the left show us the number of flats in that key.
For example, C has zero sharps or flats, G has 1 sharp, so that means D has 2 sharps, since it’s two notches to the right of C. A has 3 sharps and E has 4 sharps. The same rule applies to the flat side as well. The key of F has 1 flat, the key of Bb has 2 flats, the key of Eb has 3 flats.
The Circle of Fifths also show us the relative minor keys, which means they use exactly the same notes as their major key counterparts. For example, the key of C and the key of Am use exactly the same notes since they have zero sharps or flats.
If we use this same logic, we’ll also know that the key of A major shares the exact same notes as the key of F# minor because they share the exact same sharps.
Knowing the relationship between the relative minor and major keys makes it a little easier for us to play music, especially if we want to use it for understanding chord progressions. You can simply start with any note on the circle and play them in succession to create chord progressions as well, which is always a fun way to write your own song or simply practice.
For more on the Circle of Fifths, make sure you sign up for Guitar Tricks Full Access and check out this lesson the Circle of Fifths by Christopher Schlegel.