MauvePink, I humbly beg to differ on your source for that quote. It was not Louis Armstrong who made the "horses" remark. It was the Georgia/Chicago blues musician Big Bill Broonzy.
I don't know how the quote got attributed to Louis but it ain't right.

Old Vermin, an argument could be made that much of the Court music of the Antiqua derived from the music of the Trouveres (early wandering troubadours). Some of it may have been pretty close to a folk tradition although I take your point about it being highly specialized for royalty.

Autumn Leaves, music by Jacques Prevert, lyrics by Johnny Mercer.

An avocado sandwich might be folk music if devoured by a noisily chewing and famished
folk singer. :)