^You got me, but the other guesses are incorrect
The reason I chose Scarborough Fair and Greensleeves is that aside from that I think they are nice songs, they are both (english) medieval ballads. Both these songs have been recorded by a multitude of artists from cheap techno versions to chilean pan-flute artists to sarah brightman and Frank Sinatra. Greensleeves is even known as a christmas tune I think in America, although I don't know how that first started.
Anyways, Scott Williams' Greensleeves is a good version and it sounds pretty medieval-ish to me. Simon & Garfunkel's take on Scarborough Fair is also good, I think. They've certainly done it with a medieval twist. It even sounds a bit like they've taken inspiration from gregorian chant which was an important musical expression or whatever you call it in medieval times.