In [music theory](Music%20theory.md), the circle of fifth is ==a way of organizing the 12 chromatic pitches as a sequence of perfect fifths==. It's at the foundation of the western tonal music as we know it today and seems to western people the most harmonious way of arranging pitches. Some sources converge to say that it's Pythagoras that invented the circle of fifths in the sixth century B.C as he made a lot of works on harmonic and invented a system of tuning based upon the interval of a fifth. If we read it clockwise from C, it goes : ``` C G D A E B F# C# G# D# A# F(E#) C(B#) ``` By moving up by fifths (or going down by fourths), we're going on brighter and brighter chords until we reach the maximum of sharp in a key signature with the C#. Counterclockwise : ``` C F Bb Eb Ab Db Gb Cb(B) E A D G ``` Here, we're mouving down by fifths (so up by fourths) and going darker and darker until we reach the Cb key signature.  ## Usage Knowing how the circle of fifth work allows musician to compose music and perform modulations. It also give us the number of # or b for the key signature. When you want to modulate from a key to another, the best and easy sounding way of making this is going either to the left or right of the circle of fifth. I.e : you're in C major and want to modulate, you can choose to go on G major or F major, it will sound great no matter what. By going by fourths (so counterclockwise on the circle), we also end up having a chain of [Perfect cadencies (V-I)](Chords%20progressions.md#Perfect), which is great to know how you can create tension and release in a song. Admitting you still want to modulate from C to G by inserting the V degree of the key center you're moving to, you know by watching the circle of fifth that you would use a D to achieve that. The V-I will make everything obvious as you're bringing the tension from it's V degree to release on the I you're going to. We can say that the V is here to justify the modulation and having something smoother. ## More on this There's this masterclass from Jacob Collier, full of new ways of seeing how do you move through chords within the circle of fifths : <iframe width="100%" height="415" src="https://www.youtube.com/embed/mLJVvjqMjbo" title="YouTube video player" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>