Notes and Scales: Chapter 4 – The Circle of Fifths (Understanding Basic Music Theory)
4.7 The Circle of Fifths
4.7.1 Related Keys
The circle of fths is a way to arrange keys to show how closely they are related to each other.
Figure 4.44: The major key for each key signature is shown as a capital letter; the minor key as a small letter. In theory, one could continue around the circle adding ats or sharps (so that B major is also C at major, with seven ats, E major is also F at major, with 6 ats and a double at, and so on), but in practice such key signatures are very rare.
Keys are not considered closely related to each other if they are near each other in the chromatic scale (or on a keyboard). What makes two keys “closely related” is having similar key signatures (Section 1.1.4). So the most closely related key to C major, for example, is A minor, since they have the same key signature (no sharps and no ats).
This puts them in the same “slice” of the circle. The next most closely related keys to C major would be G major (or E minor), with one sharp, and F major (or D minor), with only one at. The keys that are most distant from C major, with six sharps or six ats, are on the opposite side of the circle.
The circle of fths gets its name from the fact that as you go from one section of the circle to the next, you are going up or down by an interval of a perfect fth (Section 22.214.171.124: Perfect Intervals).
If you go up a perfect fth (clockwise in the circle), you get the key that has one more sharp or one less at; if you go down a perfect fth (counterclockwise), you get the key that has one more at or one less sharp. Since going down by a perfect fth is the same as going up by a perfect fourth, the counterclockwise direction is sometimes referred to as a “circle of fourths”. (Please review inverted intervals (Section 4.5.4: Inverting Intervals) if this is confusing.)
The key of D major has two sharps. Using the circle of fths, we nd that the most closely related major keys (one in each direction) are G major, with only one sharp, and A major, with three sharps. The relative minors of all of these keys (B minor, E minor, and F sharp minor) are also closely related to D major.
What are the keys most closely related to E at major? To A minor?
Name the major and minor keys for each key signature.
4.7.2 Key Signatures
If you do not know the order of the sharps and ats, you can also use the circle of fths to nd these. The rst sharp in a key signature is always F sharp; the second sharp in a key signature is always (a perfect fth away) C sharp; the third is always G sharp, and so on, all the way to B sharp.
The rst at in a key signature is always B at (the same as the last sharp); the second is always E at, and so on, all the way to F at. Notice that, just as with the key signatures, you add sharps or subtract ats as you go clockwise around the circle, and add ats or subtract sharps as you go counterclockwise.
Figure 4.44 (Circle of Fifths) shows that D major has 2 sharps; Figure 4.46 (Adding Sharps and Flats to the Key Signature) shows that they are F sharp and C sharp. After D major, name the next four sharp keys, and name the sharp that is added with each key.
E minor is the rst sharp minor key; the rst sharp added in both major and minor keys is always F sharp. Name the next three sharp minor keys, and the sharp that is added in each key.
After B at major, name the next four at keys, and name the at that is added with each key.
Basic Music Theory