Besides a tendency to abstractness. inherent in the technical nature of the subject itself. a common problem in the teaching of medieval music history is how to awaken the interest of learners in matters that are so far back in time as to have nothing in common with modern sensibility. Referring to the introduction of the staff by Guido of Arezzo in the 11th century. https://www.roneverhart.com/Oakley-SI-Holbrook-Multicam-Men-s-Lifestyle-Polarized-Sunglasses-Brand-New/