I'll be more inclined to accept people as having something to contribute to a discussion about the meanings of words when they can spell "usurp".

Plainly, to those who can read, the 1954 definition is not culture-specific. Hence (apart from the issue of known authorship) most Delta Blues is American Folk music, while what the Coppers do is English Folk music, and more or less the same applies in respect of the Balkans, etc, and a wide range of African Folk music.