There's even national or regional variations in lilting a tune - for instances when you're just singing a tune with no words as such would you tend to go "la, la, la" or "di diddle de"

You may be confused by a reference to thread creep in my message of 22-May-02 . This is the thread which I re-pasted the discussion into and I forgot to remove the now irrelevant sentence in the brackets.

LD, 03-Nov-00, wrote There's a Scots Gaelic song tradition called puirt-a-beal (mouth music) - this is primarily music for dancing to (though I've heard a theory that it originated on the islands as a way to while away the long working hours).
This "theory" is a confusion between the mouth music songs for dancing and the waulking songs for group work fulling tweed. The latter have very regular alternating refrain lines and the function is not dissimilar to the refrains in shanties. And yes, the singing did keep up the spirits of the women as they worked. I have spoken to women in the Western Isles of Scotland who waulked tweed when they were young and although the work itself was tedious, they enjoyed the social aspect of the work.

This thread has several good contributions already, but I shall plug away until someone has more to say about the rex-fols that are found in both Irish and English language songs!