Circle Of Fifths

Within music theory, we have what is known as the circle of fifths. This figure represents the relationships among the twelve tones of the chromatic scale. It also shows their corresponding key signatures, and major and minor keys. Musicians sometimes use this to help with composing music. Here is a bit of background on the 12 tone Equal Temperament.

12 Tone Equal Temperament (Also known as 12TET) In order to understand some of this you will need a strong background in math. Here is the formula used to calculate the ½ steps between the tones, (The Twelfth Root of 2, which also equals the following in decimal form, “1.05946309”)
This system is currently the most widely used in the world and this is why we can all jam together using different instruments.

The standard of A-440Hz we use to tune to was established in 1939 at a conference in London. 

Understanding The Circle of Fifths

At the top of the circle we have the key of (C) each note value moving clockwise is the fifth note of that diatonic scale. If you take the fifth note of the C major scale you have (G), the second note on the circle. As we move clockwise around the circle the number of sharps and flats in a particular key are identified. Notice the key of (G) has one sharp and the key of (D) has two sharps and so on. Also, when we look at the inner circle the relative minor notes are defined. Note:The minor key starts three semi tones below its relative major. Take a look at the key of (C) major has (A) as its relative minor. The tonic of the relative minor is the sixth scale degree of the major scale, while the tonic of the relative major is the third degree of the minor scale. I hope this lesson gives you the basics in learning about the Circle of Fifths.

Here is the Circle of Fifths symbol you can use for reference, you may find it very useful depending on what you are trying to accomplish.