Scarborough Fair is a very old song, according to Wikipedia dating back at least to 1670, and probably much earlier. Here are three versions from the mid-sixties.
The first from Martin Carthy was released in 1965, on his first album:
The second,from Marianne Faithfull, was released in 1966 on the album North Country Maid:
The third, from Simon and Garfunkel, was released later the same year, and of the three is by far the best known:
I read somewhere that Carthy taught Simon the song when S&G were on tour in the UK, and that Simon then recorded the song without giving Carthy the slightest acknowledgement of his contribution, which caused bad blood between them.
I don’t know if that’s true or not but it does square with the rather callous persona that Simon has cultivated over the years.
I say that as a Paul Simon fan. He’s a great musician but I suspect a bit of a jerk.
According to one source, “Simon & Garfunkel gave Carthy no credit on their recording for the arrangement of a traditional folk song, and Carthy accused Simon of stealing his work. Many years later, Simon settled the issue with Carthy, and in 2000 they performed together in London.” , History of the Folk Song ‘Scarborough Fair’, http://www.thought.com.
Additionally, here’s a really overdone version by Hayley Westenra of Celtic Woman: