More time than not, when it says someone wrote a tune, it means they put a tune to it, without consciously copying it from another song. And I'd imagine that wouild be what happened here, in both cases.

I think it's pretty well true to say there aren't any good totally new tunes, they are all variants. Maybe that's an exageration, but I'm inclined to say it's not at all far from the literal truth.

Tunes are in the air around us.