St. Galgano was a 12th century Italian nobleman who renounced a life of violence after seeing a vision of Archangel Michael, and plunged his sword into a rock. This is apparently preserved at the ruined Cistercian Gothic abbey of San Galgano at Montesiepe, near Sienna.
Somehow this got involved with the legend of King Arthur, perhaps by the storytellers Geoffrey of Monmouth, Chretian de Troyes and others unknown, and eventually Thomas Mallory.
This brings these verses and these old tales into your period, although you will have to invent the music to accompany them. As pointed out by Leeneia in a post above, this was the usual practice with these stories. An interesting new twist to present to an audience.

The story is in the Times of London, report by Richard Owen, but unfortunately I don't have the date (very recent). The heading used in Canadian papers was "Was King Arthur really an Italian?" but I don't know how the story was headed in the Times. You should be able to run down the original article.