Since I already have a reputation for being appalling and argumentative, I will say that for me phrases like 'the oral tradition' beg not just one but several questions.

Singular noun, definite article. The linguistic choices here have significance.

Also questions of whose tradition(s) when, and whether these vary according to date, gender, ethnicity/sub-cultural group/region.

Certainly for me, a concept with all sorts of ideological associations. And presumably not always thought of in quite the same way by different people making use of it.   

Also Steve, while deferring to your expertise and experience, what may seem 'obvious' to one person might not seem so to another. For me, and this is just personal, if, while carrying out some research, I came across a piece of what purported to be 'history' (and Brian can mutter about apostrophes as often as he likes I am still putting it in scare quotes) which stated that oral influences on a piece were obvious, I like to think that I would still be looking to see what the basis for that view was, and how the point was argued.