Neumes.

Before the invention of a system for notating music in the ninth century, music was passed on from one person to the next only by aural transmission—that is, melodies were carried only in the memory, and learned by repeated hearing. A new monk, for example, would spend hours every day for several years learning by rote memory all of the chant melodies for the entire liturgical cycle, taught by the magister scholarum—the director of music. The first system of notating music was developed sometime during the Carolingian era after 800 for the purpose of transmitting information about vocal performance, the nuances of a singing style. Although this led eventually to the notation system still in use today, it did not have the same purpose as modern notation, that of presenting the basic information about pitch and duration. The earliest notes, called neumes...