I know some of you have heard of this thread before, but I need more info on this style of song. Often heard in celtic type songs, it goes something like this....

"Humm Diddle dotin da, diddle diddel day"

....something along that line!? It's used often as fill in many songs. Some call it scat, others call it mummble. For the last few years I have been developing this style. Others I meet that uses this form of mouth noise, don't seem to know the correct term. Any music teachers? I would like to research this form of song a little more.