It might be interesting to zoom out of the current perspective and consider the whole business of traditional music over a much longer timescale - just to get a different slant.

Let's say, for the sake of argument, that the keepers of the flame of traditional music in Ireland are currently singing and playing folk music that's now between 100 to 200 years old. (This isn't supposed to be exact, just an arbitrary bracketing to point up the discussion). Now fast forward to 2060 - let's assume the same tradition is being preserved - and the same music is now between 150 to 250 years old. Fast forward again another 50 years - and the same music is now between 200 to 250 years old.

So here we are in Ireland, in 2111. Where is the Irish music of 2011 in all that? Is there any? What 100-year old songs will be played then? What 100 year-old tunes will be played? How will they have got into the tradition? Or will only the stuff which is being performed now be the stuff that's being performed 100 years hence? If the latter is the case, then that whole music will be a permanently ageing museum piece, unchanging, mummified.

If it's not the latter - if the young Irish musician and singers of 2111 are playing and singing folk music of a 100 years ago - where's it coming from? What are the rules or formulae or recipes or conventions by which it's all kept alive and bubbling? And not just in Ireland, in any other country? I've never yet heard the answer to this question in any of the "what is folk" threads.