Dated to the late thirteenth or early fourteenth century, it represents a mixture of the Greek myth of Orpheus with Celtic mythology and folklore concerning fairies, introduced into the English culture via the Old French Breton lais of poets like Marie de France. Sir Orfeo is preserved in three manuscripts, Advocates 19.2.1 known as the Auchinleck MS. and dated at about 1330, the oldest. The next oldest manuscript, Harley 3810, is from about the beginning of the fourteenth century. The third, Ashmole 61, was compiled over the course of several years; the portion of the MS. containing Sir Orfeo is c. 1488. The beginning of the poem describes itself as a Breton lai, and says it is derived from a no longer extant text, the Lai d’Orphey. Child Ballad 19 "King Orfeo" is closely related to this poem.
In the poem, Sir Orfeo, king of Thrace, loses his wife Heurodis (i.e. Eurydice) to the fairy king, who steals her away from under an apple tree, an imp tree that happened to be haunted by the fairies, and takes her to his underworld kingdom. Orfeo, distraught by this, leaves his court and wanders in a forest. While there, he sees Heurodis riding past in the company of the fairy host. He follows them to the realm of the fairy king, where he entertains the fairy king by playing his harp. The fairy king, pleased with Orfeo's music, offers him the chance to choose a reward; he chooses Heurodis. Orfeo returns with Heurodis and reclaims his throne.
While this is not the classical myth of Orpheus, the poet shows substantial ingenuity in merging the Orpheus of mythology, who tries and fails to obtain the return of his wife Eurydice from Hades, the realm of Pluto, with the traditional Celtic fairy motifs of the fairy rade or hunt, the fairies' underground kingdom, their attempts to abduct mortals, and the magical transformations endured by those who are captured by them. These motifs are shared by both Sir Orfeo and later-collected versions of Celtic ballad fairy-lore in such works as the ballads of Thomas the Rhymer and Tam Lin. =References=