They also relate to the Quadrivium. Gregorian chant and miniatures are examples of the practical application of quadrivium subjects. The "quadrivium" consisted of arithmetic, geometry, music, and astronomy. This is the origin of the quadrivium&colon; arithmetic, geometry, astronomy, and music. Within the quantitative Quadrivium, music, or more accurately harmonics, was the study of rational proportions. Secondary education, classically the "quadrivium" or "four ways," consist of arithmetic, geometry, music, and astronomy. He did not study any subjects beyond the trivium and quadrivium at these schools. In 2013, the couple launched Quadrivium Foundation. Courses of study are inspired by the classical trivium and quadrivium. The study of number comprising the four arts was later called the "Quadrivium". The book covers the Quadrivium in a detailed and skilled fashion. The quadrivium consisted of arithmetic, geometry, music, and astronomy.