A few more things to consider:
http://www.youtube.com/watch?v=FzDC4284 ... re=related
So John Martyn does justice to `Spencer the Rover', whoever he was, written nonetheless by someone about someone; something real that actually happened, or close to it a long time ago.
And Traffic did justice to `John Barleycorn' whoever he was, but actually not anyone at all, but just a concept; written I'm sure a lot earlier than ` Spencer the Rover, but still written at some time essentially by some one.
And Sandy wrote `Who Knows Where the Time Goes' ; which if she'd writ ( if such could have been done) 200 years earlier, we'd all know as `Traditional or anonymous'....