I have just been reading Lajos Vargjas's Folk Music of the Hungarians (2005 ed) and came across these quotes from Bartok, writing in 1942. They are relevant to a couple of long-running threads here.

Folk music in East Europe can be summed up as follows: as a result of incessant interaction among the folk music of all the peoples, an immense richness of tunes and tune types has arisen. The resulting racial impurity is therefore most beneficial.

Keeping aloof of foreign influences entails stagnation: well-assimilated foreign influences give rise to enrichment.

Contact with foreign material, however, does not merely result in an exchange of tunes but, more importantly, it also stimulates to create new styles. At the same old and less archaic of styles also survives, providing material for the further enrichment of music.

And he quotes this from Bartok's The Hungarian Folk Song, published in English translation in 1981, on the"new style" folk songs that mushroomed in the late 19th century:

The peasantry of Hungary preserved the idiosyncrasies of old native music, but were not hostile to innovation: hence the birth of the new style which is altogether homogeneous, quite different from that of any other peasant music, typical of the race, and closely connected with the no less typical old style. There is, to my knowledge, no other country in which, of late years, a similarly homogeneous new style has cropped up. And the originality - even the existence - of this new Hungarian style is all the more astonishing when one considers that so many alien elements had penetrated into Hungary before this style began to take shape. That these alien influences did not seriously interfere with the national character of Hungarian peasant music at the new stage of evolution is the best possible proof of the independence and the creative power of the Hungarian peasantry.