RILM abstract: "A comparison of the "ornamental" neumes in the earliest notation with theoretical statements about their execution shows a close relationship between the shape of the neumes and the intended sound. This suggests that one of the primary purposes of the earliest notation was to transmit information about the performance of vocal gestures and nuances that were unfamiliar to the northern Europeans."
McGee, Timothy J.
""Ornamental" Neumes and Early Notation,"
Performance Practice Review:
1, Article 5.
Available at: https://scholarship.claremont.edu/ppr/vol9/iss1/5