Musical notation was used by Hildegard of Bingen (1098-1179) so in its various forms is at least 1000 years old. Did the Romans have notation for tunes played on the hydraulus (organ) or did each performer apply his own music?

Examples

As pointed out by Dave Bryant, literacy was rare in the 11th-16th c. so written or notated music is not really folk.

Religious music excluded? This would, in America, leave out the spirituals.

Thanks, Stilly R S, for Pound's parody. I had lost my copy.