Totally agree with Steve on football chants. They satisfy the kind of definition of 'traditional' that I would prefer, namely 'that which is handed on'. When I learned 'You'll Never Walk Again' (as the Old Trafford version had it) on the terraces, I'd certainly never heard of Rogers & Hammerstein (I'd be equally sure my sons have never heard them either). You learned the chants from other people in the crowd, or sometimes rival supporters, never knew where they came from, sometimes recognized the original source song and sometimes not. Just like we all learned 'I went to the pictures tomorrow' and 'We four Beatles of Liverpool are' in the school playground.

The problem of discussing definitions like this is that the phrase 'traditional song' is often used within the folk music world to denote the kind of song that Cecil Sharp and his ilk liked to collect, i.e. songs of 17th-19th century coinage that had passed into oral tradition by the late 19th and early 20th century. In the world of 2010, those songs are no longer 'traditional' in the sense of continuing to be handed down within families and local communities, although they are still performed on the stages of the folk music world. They have broadly recognizable lyrical and musical characteristics and (to my mind at least) form a body of repertoire separate from, say, music hall material, which has different and usually easily recognizable characteristics of its own. So I still sometimes use the term 'traditional song' to describe that body of older material, even though - in academic terms - 'You'll Never Walk Alone' or 'Happy Birthday to You' satisfy the definition of 'traditional' much better in the contemporary world. Doesn't mean I want to hear football chants sung in folk clubs, though.

As to 'traditional singer', again this is a specialised usage among insiders discussing the history of vernacular or 'folk' song. This definition too is very difficult to pin down, mostly because the growth of mass media over the last 100 years has gradually turned us from a society in which entertainment amongst the less privileged classes was largely home-made, to a society of much more passive consumers. However, this has been a gradual process, so even today we still find individuals within certain communities (travellers spring immediately to mind) who still make and hand on music for their own entertainment. Meanwhile, the traditional singers of the 20th century - by which I mean those who learned songs within the family (the great majority of the singers on 'Voice of the People' for instance) were able to augment their family repertoires not only from social acquaintances, migrant workers and so forth - as they'd always done - but from the radio, records or (in a few cases) from the folk revival which had invited them onto its stages. That Fred Jordan should have picked up songs at folk festivals is no more surprising than that he should have learned songs from the gypsies working in the fields around his home.

Given that 'traditional song' and 'traditional singer' have specialised meanings depending on the context in which they're being discussed, it's perhaps not so surprising that we can find ourselves in a situation where a 'traditional singer' doesn't necessarily sing 'traditional songs'.