What is the Circle of Fifths?

In music theory, the circle or cycle of fifths (also known as the circle of fourths) is a sequence of notes spaced by intervals of a perfect fifth (clockwise) or a perfect fourth (counterclockwise).

Example

The sequence: C - G - D - A - E - B is formed by intervals of a perfect fifth.

Note that B is a fifth above E, and E is a fifth above A, and so on.

Also note that by reversing the sequence (B - E - A - D - G - C) we have intervals of a perfect fourth, meaning that from B to E we have a perfect fourth interval, and from E to A we also have a perfect fourth interval, and so on.

What is it used for?

The study of the circle of fifths can facilitate the understanding of key signatures, scales, key transposition, and harmonic fields.

Basic Use

The circle starts with the C Major key selected.

Note that we have highlighted exactly the notes of the C scale: C, D, E, F, G, A, and B.

We can also observe that none of these notes have alterations (sharp or flat), which determines the key signature of C.

If we analyze the degrees, we will see that we can build the harmonic field from this analysis.

It is also possible to transpose the key by observing the position of the degrees.

The neighboring circle will always have a large number of notes in common.

Turning the circle clockwise adds sharp accidents.

Turning the circle counterclockwise adds flat accidents.

Applications of the Circle of Fifths

• Scale Construction: The circle of fifths is crucial for constructing major and minor scales. It helps to visualize the order of sharps and flats in each key.
• Composition and Harmonization: Composers use the circle of fifths to create harmonic progressions that sound natural to the ear. Common progressions, such as I-IV-V, are easily identified in the circle.
• Transposition: Musicians who need to transpose a piece from one key to another can use the circle of fifths to find the relationship between the notes of the two keys.

Conclusion

The circle of fifths is an indispensable tool for any musician. It not only facilitates theoretical understanding of music but also provides a solid foundation for musical practice. Whether in composition, performance, or improvisation, understanding and applying the circle of fifths can transform a musician's approach to harmony and melody.