Peter Hollens and Avi Kaplan, "Black Is the Color of My True Love's Hair". This is a traditional folk song, with lots of versions. It was first recorded in Appalachia in the early twentieth century, but there are vocabulary indications in early versions that suggest it was brought over much earlier from Scotland. The most famous version is probably
that of Nina Simone, although it has become standard fare in Celtic music circles, as in
Lisa Lambe's version for Celtic Woman, which is fairly good.