Barzas-Breiz

Below is the Britannia entry for Barzas-Breiz. I hadn't come across this Breton collection before, but it has an interesting comparison with the inventions of Iolo Morganwg, James McPherson ("Ossian") and some of the Irish material. I've learned to be very postmodern about these things by now, and I consider these to be as much a continuation of the traditions as they are forgeries.

Barzas-Breiz; Chants Populaires de la Bretagne (“Breton Bardic Poems: Popular Songs of Brittany”) collection of folk songs and ballads purported to be survivals from ancient Breton folklore. The collection was made, supposedly from the oral literature of Breton peasants, by Théodore Hersart de La Villemarqué and was published in 1839. In the 1870s it was demonstrated that Barzaz Breiz was not an anthology of Breton folk poetry but rather a mixture of old poems, chiefly love songs and ballads, that were rearranged by the editor or others; modern poems made to look medieval; and spurious poems about such romance figures as Merlin and Nominoë. Review of Villemarqué's papers in the 1980s, however, showed that some of the poems were authentic.

Barzaz Breiz was extremely influential: the historical poems exalting the Bretons' traditional struggle against oppression revived Breton pride in their language and heritage; it also led to the reawakening of Breton writers and stimulated further study of Breton folklore.

http://www.britannica.com/eb/article-9013566