Circle of Fifths

The "Circle of Fifths" is a geometrical construction, where all of the notes in the octave are layed out in such a way that the distance from note to note is a 5th, or 7 semi-tones.

Starting from C at the top, we place G (which is one fifth intervals apart, or 7 semitones) to its right, followed by D, A, etc.

The sequence of notes goes by fifths when looking at it clockwise (C-G-D-A-etc).

When looking counter-clockwise, it goes by fourths (C-F-Bb-Eb-etc).

The Circle of Fifths is used to create chord progressions.

In generic terms, as an abstraction, chord progressions are referred to by using Roman numerals. Each number refers to a scale degree. Upcase Roman numerals are used for major chords, and lowcase for minor chords.

Simple folk songs, and many classical melodies, were traditionally based on only three chords : I (tonic), V (dominant), and IV (subdominant).

For the scale of C, these chords are: C (tonic), G (dominant), and F (subdominant). For any tonality, the I-IV-V chords are adjacent to each other in the Circle of Fifths.

A progression based on three chords can be: I-IV-I-V-I.

It can be seen in the circle as oscillating back and forth around the Tonic chord.

Example in the key of E major: E-A-E-B7-E.

[The number written next to the Roman numeral denotes a chord alteration, usually chosen to match the current scale.]

Another famous progression is the : I-VI-II-V-I.

It can be seen in the circle as a 1/3 circle's jump forward, followed by three single counter-clockwise steps, back to home.

For any major scale, this progression is abstractly referred to as: I-vi-ii-V-I.

For the key of C major, this chord progression could be: C-Am7-Dm7-G7-C.

Refer to the circle to see how easy transposition can be made: In the key of G, this chord progression would be: G-Em7-Am7-Dm7-G.

Counter-clockwise movements create a progression by fourths, and it has the feeling of resolving each chords tension into the next chord.