Ballads and Songs of Brittany: Translated from The "Barsax-Breiz" of Vicomte Hersart De La Villemarque, with Some of the Original Melodies Harmonized by Mrs. Tom Tayor Paperback – 23 Nov. 2017

This is known as Barzaz Breizh in Brittany. It is considered a classic collection of folk songs in Brittany, although there is some argument over how "authentic/traditional" some of the songs are in actuality. Nonetheless, if you are interested in breton folklore then this is a great treasure. However you should note that at least in this English translation edition, most of the songs do NOT have the actual music presented for them, just the lyrics translated from the Brezhoneg or French into English by Tom Taylor in 1865. And I have not checked what liberties were taken by his wife in "harmonizing" those few tunes. Nonetheless, for English speakers interested in breton folksongs, this is a worthwhile book, even if it is just a scanned version of the original.