I read this book in 1978 but can't remember title or author.Possibly a young adult novel. Plot is based on lyrics of Scarborough Fair where a young soldier from the past (Civil War?) Visits a girl in the present to perform the "tasks" of the song.
I've been trying to trace it for many years now with no luck. Searches often suggest Nancy Werlin or Rebecca Jane Curry but these are not what I'm looking for.