The answer to this is Nationalism itself underwent a transformation in the nineteenth century,
in that during the first half of the century, a “nationalist” was also a
“citizen of the world”, but by the latter half of the century nationalism
had turned much more aggressive, with the oppressing nations initiating this
change. Unfortunately, the attitude of the oppressed was equally affected
by this. As nationalism matured, in music the change is apparent in works
written primarily after 1860. It is for this reason that serious consideration
must be given to the fact that various types of political evolution were
achieved in each country that in turn affected musical nationalism.
I hope this helps!!!!!
