Okay,
for those who think the 54 description is outmoded or irrelevant:-

Amongst many other users of the words 'Folk Songs' are book editors and book buyers (nothing to do with academia). One of the most prestigious and sought-after anthologies to be produced recently in the English-speaking world is 'The New Penguin Book of English Folk Songs'. It has no subtitle using the words 'traditional' or 'vernacular'. As far as I can see it has no songs in it written after 1900, and precious little in fact written after 1800. Also as far as I can see all of the material conforms to 54.

I don't remember anyone complaining about the usage of this title. Should the book have had a different title? Admittedly it was regurgitating a title first used in 1959, only 5 years after the definition.

I'm not trying particularly to defend 54 but just out of interest adding to the discussion. It's alright saying it is outdated etc. so then what would you alter?