Even waves — odd circles refers to even harmonics making waves and odd harmonics completing circles. Harmonics are inherent vibrations at a positive integral multiple frequency of corresponding fundamentals. In music, harmonics are the pure tones that make up sounds as composites of a fundamental and its partials or overtones. How even harmonics make waves and odd ones complete circles is shown in Harmonics Base and the Realization Shift, the second module of the five-part course series Harmonic and Tonality Fundamentals.