I suggest you might wish to have a look at:
http://en.wikipedia.org/wiki/Lilting
Lilting has become an art form in its own right thanks to the likes of Paddy Tunney et al, but it can also occur either in the middle of a song - for example when Lasairfhíona Ní Chonaola does in the song 'Bean Pháidín' (CD An Raicín Álainn) because she is obviously enjoying the melody of the song - or at the end where the singer has run out of verses and wants to keep on singing. And of course there is the use of lilting as an easy chorus for the audience to join in. In traditional English folksong it turns up sometimes as a kind of (sexual) innuendo - hey nonny no etc. - and used for growing effect as the song continues. But I can also give an example where the (meaningless) lilting changes into words. This is taken from 'Féidlim Tonn Rí's Castle' as told by Seamus Ennis (in English but transposed directly from Irish) He begins lilting to illustrate what he is describing and then goes on to put words to the tune.
'Dee umpty dee ay dee....
-That was an old thing....
Cold potatoes, cold potatoes
Salt and dip it in
Salt and dip it in
Cold potatoes, cold potatoes
Salt and dip it in
Good for the King
-that kind of thing, as the ball was rolling and hopping on the rough ground, and he followed it all day until nightfall.'
This must have been a common practice in Irish Gaelic storytelling in the past, though I don't know if it is still the case.
In Scottish Gaelic the tradition of Puirt a Beul consists not only of playing around with the sounds of words (as pure nonsense) but also for making funny remarks about neighbours or family members.
www.Itscotland.org.uk/ng/resources/musi ... gaelic.htm
-scroll down to: Listening to mouth music, and how to make it (and click to listen)
My favourite examples of Puirt a Beul are Julie Fowlis (CD Cuilidh) -'S Toigh Leam Fhín Buntáta 's Ím -you can just imagine the old man dancing spritely a strathspey around the room in front of everyone, singing that he likes potatoes, butter, ladies and the young girls of the village and the merriment that must have provoked; and Finlay spreading manure and nearly getting killed by Máiri carrying a load of hay. 'Húg air a' Bhonaid Mhóir', Puirt a Beul sung by Sileas (CD Beating Harps), and 'Fionnghuala' by the Bothy Band (CD Old Hag you have killed me).
All the words are available from
www.celticlyricscorner.net
Julie Fowlis sings with Muireann Níc Amhlaoibh
www.youtube.com/watch?v=raOhfgsft81&feature=related
plus
www.youtube.com/watch?v=1XUTuxSHRUY&feature=related
www.youtube.com/watch?v=w1I2nCAaodI&feature=related
www.youtube.com/watch?v=wX18CMR1I9Y
Lastly I would like to point out that there is another dimension to all this oral culture that I think is so important, and that is the oral traditions of children. Very often it has been found that children must have been present when adults were singing and subsequently picked up a daring couplet or two and adapted it to their own needs; taking delight in the sound, the nonsense aspect or just taking 'forbidden fruit' shall we say.
I'm sorry that this is a bit long, but as you can see this is a subject that I'm interested in.
Slán Franc
PS I can well sympathise with BridMhor and her fridge