It's true that many songs and tunes are of mixed ancestry, and that some get taken up by another race or nation who adopt it as their own. Eventually the origins of the song or tune can get lost in a fog of myth and rumour. Does this matter?

In many cases, no. But I get irritated by the one-sided "Irish jingoism" mentioned by Jack, above; it's not always perpetuated by the Irish, but often by sentimental pseudo-Irish sympathisers who belong to another nation. It leads to silly assumptions and misattributions. I don't know of any other musical tradition that gets tunes and songs wrongly attributed it to it so carelessly and so often.

In a more general way, the origin of a song or tune matters to the many singers and musicians who take a real interest in the sources of their material, and like to know how and why a piece of music came into being, and how it's been used over the years. If you don't care about any of this - fine, just enjoy the tunes and songs as you find them; but many people find it rewarding to try to understand the various styles of composition and playing that are charateristic of different times and places. Many musicians also care about attributing their material correctly, and think it only fair to acknowledge the composer, particularly if it's someone still alive.

So although a song or tune may not have a fixed "nationality", it may well have a known origin or composer associated with a particular country, and many people like to know about this background and acknowledge it.

Marje