Here is Fleetwood Mac performing Rhiannon live in 1976. Singer / songwriter Stevie Nicks discovered Rhiannon through a novel called Triad, by Mary Leader. The novel is about a woman named Branwen, who is possessed by another woman named Rhiannon. There is mention of the Welsh legend of Rhiannon in the novel, but the characters in the novel bear little resemblance to their original Welsh namesakes (both Rhiannon and Branwen are major female characters in the medieval Welsh prose tales of the Mabinogion).
Nicks bought the novel in an airport just before a long flight and thought the name was so pretty that she wanted to write something about a girl named Rhiannon. She wrote “Rhiannon” in 1974, three months before joining Fleetwood Mac, and has claimed that it took 10 minutes to write. After writing the song, Nicks learned that Rhiannon originated from a Welsh goddess, and was amazed that the haunting song lyrics applied to the Welsh Rhiannon as well.
A stripped down vocals & piano version & the original version were featured in the 3rd season of American Horror Story aka Coven.