The notion of pitch, i.e. the opposition of high and low, altitudo sonorum, is essential to the development of Western musical writing; it associates a visual element, high and low, with sound. Pitch exists in neumatic notation without conceptualization A convergence of facts suggests that the concept of musical pitch was developed in the 9th century in the schools associated with John the Scot, also known as the Eriugena, under Charles the Bald, in a re-thinking of the world view and a reinterpretation of the science bequeathed by scholars of antiquity.