"So if a musical group of Polish immigrants in Dublin, London or Glasgow are singing Polish folk songs, or dancing Polish dances in Polish national costume,"
They become part of those places' street traditions and are worthy of being archived as such - as were |London street musicians (German musicianers) in the 19th century) immigrants have always brought their songs with them and, if they settle anywhere, those songs become part of that tradition (if there is a living tradition to absorbe them).
Bit of an upside down argument anyway
Raglan Road is a poem by Patrick Cavanagh and Dirty Old Town is a modern song written by Ewan MacColl - neither are traditional songs from anywhere.
Jim Carroll