Has anyone ever found anything that even slightly resembles written musical notations during the early Roman Empire? - Quora
Visigothic chant--Aleteia
Gregorian Chant Lovers
Salve Regina (Simple Tone) - Gregorian Chant
A comparison between Gregorian Chants and Motets - HubPages
Gregorian Chant Notation: Solfege - Catholic Living
Lord's Prayer - Wikipedia
Chopin: A Progressive in Tonality - The Boston Musical Intelligencer
Gregorian Chant Lovers