ca. 795–800 – Tonary of St Riquier, the earliest Western source organized according to the eight Gregorian modes, borrowed from the Byzantine octoechos system[4]
9th century – Notker the Stammerer explains the supplementary letters for neumatic notation in his Epistola ad Lantbertum[5]
ca. 850 – Aurelian of Réôme writes the earliest extant medieval treatise on music, Musica disciplina[6]
Apel, Willi. 1958. Gregorian Chant. Bloomington and London: Indiana University Press.
Bellingham, Jane. 2001. "Aurelian of Réôme [Aurelianus Reomensis]". The New Grove Dictionary of Music and Musicians, second edition, edited by Stanley Sadie and John Tyrrell. London: Macmillan Publishers.
Bower, Calvin. 2001. "Boethius [Anicius Manlius Severinus Boethius]". The New Grove Dictionary of Music and Musicians, second edition, edited by Stanley Sadie and John Tyrrell. London: Macmillan Publishers.
Chartier, Yves. 2001. "Hucbald of St Amand". The New Grove Dictionary of Music and Musicians, second edition, edited by Stanley Sadie and John Tyrrell. London: Macmillan Publishers.
Clark, James Midgley. 1926. The Abbey of St Gall as a Centre of Literature and Art. Cambridge: The University Press.
Erickson, Raymond. 2001. "Musica enchiriadis, Scholia enchiriadis". The New Grove Dictionary of Music and Musicians, second edition, edited by Stanley Sadie and John Tyrrell. London: Macmillan Publishers.
Hiley, David. 2001. "Notker". The New Grove Dictionary of Music and Musicians, second edition, edited by Stanley Sadie and John Tyrrell. London: Macmillan Publishers.
O'Connor, John Bonaventure. 1910. "St. Isidore of Seville". The Catholic Encyclopedia, vol. 8. New York: Robert Appleton Company (accessed 12 September 2014).
Planchart, Alejandro Enrique. 2001a. "St Gallen". The New Grove Dictionary of Music and Musicians, second edition, edited by Stanley Sadie and John Tyrrell. London: Macmillan Publishers.
Planchart, Alejandro Enrique. 2001b. "Tuotilo [Tutilo]". The New Grove Dictionary of Music and Musicians, second edition, edited by Stanley Sadie and John Tyrrell. London: Macmillan Publishers.
Pöhlmann, Egert, and Martin L. West. 2001. Documents of Ancient Greek Music: The Extant Melodies and Fragments. Oxford: Clarendon Press. ISBN0-19-815223-X.
Powers, Harold S., and Frans Wiering. 2001. "Mode, §II: Medieval Modal Theory". The New Grove Dictionary of Music and Musicians, second edition, edited by Stanley Sadie and John Tyrrell. London: Macmillan Publishers.
Reckow, Fritz, Edward H. Roesner, Rudolf Flotzinger, and Norman E. Smith. 2001. "Organum". The New Grove Dictionary of Music and Musicians, second edition, edited by Stanley Sadie and John Tyrrel. London: Macmillan Publishers.
Richter, Lukas. 2001. "Ptolemy [Klaudios Ptolemaios; Claudius Ptolemaeus]". The New Grove Dictionary of Music and Musicians, second edition, edited by Stanley Sadie and John Tyrrell. London: Macmillan Publishers.
Sanderson, Warren. 1982. "Archbishop Radbod, Regino of Prüm and Late Carolingian Art and Music in Trier". Jahrbuch der Berliner Museen 24:41–61.
Weakland, Rembert. 1956. "Hucbald as Musician and Theorist". The Musical Quarterly 42, no. 1 (January): 66–84.