Bruce O's tried-and-true criterion strikes me as useful in the sense that a given group of musicians (amateur or professional) might indeed distinguish 'new' from 'old' in the works that they perform. For example, Flora Thompson's semi-fictionalized autobiography, "Lark Rise to Candleford" describes a singing-session in a Victorian English small-town pub. The evening begins with the young unmarried men singing show-tunes and other popular songs. It ends with the old men singing 'summat as has stood the test o time' -- namely Child ballads. But there might be other situations where the distinction between new and old is not made.

Bruce O.'s "always-always-always" non-literate transmission criterion strikes me as less useful. It could lead to making absurd distinctions between versions of a song. Suppose singer A learns a song by having it sung to him repeatedly until he remembers it, while singer B learns another version of the same song but writes it down in order to help himself learn it. The non-literate transmission criterion would require us to put up a phoney wall between the two versions, calling A's version "traditional" or "folk" or "authentic" and the B's version "literary" or "inauthentic". In a literate society, both hearing and writing are part of the transmission process, and the fact that a song has been transmitted by one means or the other, or by a mixture of them, should not be used as a basis of classification unless different transmission routes can be shown to have made a difference to the end product.