Circle of thirds

In music theory, the circle of thirds, also known as the cycle of thirds, is a way of organizing pitches, and a musical tool that helps musicians remember and memorize the order of thirds in a scale, and hence the notes of the chords in those scales. The circle of thirds is not as well known or as versatile as the circle of fifths, but it can still be a valuable concept for musicians to know.^[1] For example, the cycle of thirds is inherently important to chord construction, as most triads are built on the cycle of thirds.^[2]

Because the circle of thirds is based on the order of thirds in a scale, rather than its ascending scale degrees, the scale degrees of the cycle are in the following order: 1-3-5-7-2-4-6. In the key of C, the order of notes will be C-E-G-B-D-F-A. However, when in another key than C, the order won't start from C, but will still be the same overall order when seen as a circle. For example, for A minor is: A-C-E-G-B-D-F.^[1]