"I'm afraid you're on your own there as you seem to know what it is"
Not really Jim I have several bookcases full of books telling me exactly what it is and have spent forty years talking to source singers who knew exactly what it is - in return I have been told there are hundreds of alternatives - so far - not one other than the old Humpty Dumpty "words mean what I say they mean" (to paraphrase.)
"over the years and never found any of them make any attempt to categorise songs"
Then our experiences differ - I have put up chunks of direct quotes from Walter Pardon, Tom Lenihan, Mikeen McCarthy and Mary Delaney, and have explained in full Mary's attitude to her non-traditional songs so unless you would like to suggest I made it all up or fed these people their scripts.....
Our work is all publicly archived with full access (though the British Library seem to be taking their time to get their arses into gear) - it's all out there somewhere.   
If you believe this thread is not for discussing such matters, then stop discussing them - or have you gone down with a nasty dose of "last wordism?"
Jim Carroll