'A tradition is a cultural thing, that a lot of people have made an input into over generations. Either by modifying the thing( whatever the thing is), or just by using it and cherishing it.

It is the modification and collective use and ownership of something that makes it traditional,' (See Greg above)

I hope we avoid the 'all music is folk I never heard a horse sing' discussion. I think Greg's offer of a definition is pretty close to what most people who have thought about traditional songs and tunes could agree with.

Is the term 'Source Singer' new? It seems to mean a singer who is singer songs from within a living oral tradition. Is this correct?

Source Singers, like those Sharp et al collected from, song all sorts of songs and so do current source singers.

The Irish Tradition is less bothered and I guess most of us aren't that concerned so long as songs are good and sung well.

But traditional songs are a bit different and a bit special. Sometimes people get carried away with this. See the thread on Mummers Plays. People claim all sorts of history with almost no evidence and sometimes none at all.