It's not hard actually...MtheGM made a good start back up there a ways when he said "I can tell instantaneously what DOESN'T sound like.., "

So...everyone go to the Mudcat/Digital tradition database and make a list of songs we agree are 'traditional'.....then we compare lists and merge the lists into one BIG list that almost everyone agrees on.

This is approximately what philosophers/semanticists call an "Ostensive_definition"
Then we make a list of what characteristics the items on the list seem to share. (Yes...that list will no doubt be similar to what several folks have already noted.)

Then, if further clarification is needed, we all turn on the television or local radio station and make a list of those 'songs' we do NOT think are "trad" and extract the common attributes.

With these two lists and some common sense, we can have a reasonable working definition, bearing in mind that someone will always point to some song...(or version of a song) and harrrumph that it is in a gray area. Sure....so what? Life is full of categories and their gray areas!

The point is, 'ostensive defintion' is how we operate most of the time, even IF our lists are not identical....and all practical applications of ostensive definition are done from someone's subjective viewpoint...(usually to sell something or defend singing a song in a certain venue...Hmmm? ☺

Most other definitions are 'intensional'... "An intensional definition, also called a connotative definition, specifies the necessary and sufficient conditions for a thing being a member of a specific set."...but many intensional definitions begin AS ostensive lists like I describe.

Ok....you may now resume debating over where to point.....