Notes on sean-nós, Irish 'big songs' and Appalachian 'high lonesome' ...

A primer on Irish Song Tradition by user Derfel on the Everything2.com website. Excerpts:

To generalize about the Irish song tradition - or even, perhaps, to call it the "Irish" song tradition - is difficult. There are obvious stylistic parallels between some Irish vocal techniques and those of, say, Western Scotland (whether it be Presbyterian hymn singing or a Catholic song of unrequited love); the "high lonesome" style of the Appalachian mountains is not a million miles away, emotionally and technically, from that of some Donegal singers; and it has become fashionable, in recent years, to suggest links between Eastern and Irish music ...

And this:

If Ireland is part of a wider cultural community, Ireland itself contains differing communities. It is likely that a particular community will have built up a repertory of song from very diverse sources, on a wide range of topics: songs of love, unrequited love, emigration, war, drinking, soldiers, sailors, tinkers, tailors; music-hall songs, blackface minstrel songs, classic "Child" ballads, songs written in praise of the locality, hedge-school compositions with intricate and absurd rhyme-schemes, nonsense songs; songs of English, Irish or Scottish origin.

The tradition, in other words, is not static, nor is it confined to one genre. A distinction is often made between so-called sean-nós singing in Irish and singing in English; yet the singer of the "big" songs in Irish may often include all of the above material in his repertory. In a night's singing in the village of Coolea in the West Cork Gaeltacht, for instance, you will hear elaborately-ornamented songs which might indeed remind one of a North Indian raga; chorus drinking songs, sporting songs, songs from the classic ballad repertory, and newly-composed songs on local incidents.

And in-between a set or two might be danced, a story told, some drink consumed. The situation, in fact, might be the genre: a context which allows a varied emotional range, in which the music and singing is itself part of an ongoing conversation, a debate between the community and itself and the concerns of the wider world.

And of course, in other communities, sectarian or "party" songs might be sung, though never, in my experience, to the exclusion of other material. ...

Also an interesting discussion of sean-nós, which I'm not qualified to judge but seems to be both contrarian and knowledgeable.