Which parts of Barzaz Breiz were found to include altered or invented material?

The Barzaz Breiz, a collection of folk songs and ballads published by Théodore Hersart de La Villemarqué in 1839, was later demonstrated to be a mixture of materials rather than a purely authentic anthology of oral folk poetry. Critics and scholars, including R.-F. Le Men and François-Marie Luzel, identified that the collection included:

• Old poems, such as ballads and love songs, that had been rearranged by the editor or others.
• Modern poems that were composed to appear medieval.
• Spurious poems featuring romance figures such as Merlin and Nominoë.

While these findings challenged the authenticity of the work, a review of La Villemarqué’s papers in the 1980s by Donatien Laurent revealed that some of the poems in the collection were indeed authentic oral literature.123