All traditional songs started out with an author, even if that person's name is unknown today. My kids learned "We All Live in a Yellow Submarine" in day camp, along with "Polly Wolly Do All Day" and "Bingo Was His Name-O," and I think that's how most kids learn it today, not from a Beatles record and certainly not from the sheet music. Does that make "We All Live in a Yellow Submarine" a traditional song? Maybe not yet, but it's more than halfway there.