It's not that I haven't got anything else to do but sit here on my computer all day, I'm just enjoying these discussions too much, and every posting engages me in another set of thought processes that I want to articulate!
I think, Graham, that you've highlighted a very interesting point. Whilst recognising that oral and literary traditions do not exist in splendid isolation, if we do want to distinguish between oral and literary traditions, then one of their distinguishing and defining features must be the way in which they use language. In terms of an oral tradition, the language is usually more informal, fluid, rhythmic, full of variations of pace, cadence, verbalised sound effects, lacking grammatical correctness, punctuated by non-verbal communication, etc, etc. In other words, the language is vernacular.
Your story about the Birmingham motor trade workers very much reflects my own feelings about the storytellers I met in the China Clay villages of Mid-Cornwall. These are communities that are very much defined by the industry that dominates them and I was amazed at the great verbal artistry of some of the people who told me stories. Within the communities I identified a number of different storytelling traditions. There were stories, inevitably, about work - particularly jocular stories about tricks being played on apprentices and stories of workers getting the upper hand against the foreman (or Mine Captain). There were also serious stories concerning work - poignant stories of tragic accidents or of unexpectedly fair and just treatment by superiors. There were another batch of stories that dealt with local characters from the past, either comically or affectionately and yet another group of stories about family forebears and their actions during the great Clay Strike of 1913, a hugely important event in the political and social history of those communities and strongly etched into the folk memory.
Some of these stories were traditional in the sense that they had been passed down through one or more generations. Some stories were reworkings of traditional stories for each new generation - e.g. traditional jokes and comic escapades being attributed to local characters. Other stories were merely recent additions to the repertoires. I would, however, maintain that all these stories contribute to a living tradition of storytelling, or rather a number of traditions, in the sense that the contexts for the telling of these stories (usually as banter at work or socially as a means of entertainment) and the types of stories told during these exchanges are traditionally determined. The stories I heard were told with great wit and skill and I was often pointed towards particular individuals who were known to have both the knowledge and the skill to be recognised as good storytellers and yarners. Like you, Graham, I consider these people to be amongst the best storytellers I have heard, even though none of them ever told me a 'traditional folk-tale'.
I would maintain that what links all the different kinds of storytelling we encounter, whether that is as low-key as conversational telling in the pub or the formal telling of a professional storyteller, is that all storytelling is a kind of performance. What distinguishes different types of storytelling is the intensity at which that performance takes place. The more intense the performance, the more the rules and conventions of performance apply. Most professional storytellers seem to operate around the top part of the scale (our performances tend to have an air of formality and consciousness above the merely conversational), whilst most everyday storytellers operate around the bottom, more informal end of the scale (my clay workers or your motor workers would probably be uncomfortable performing to a room of 100 or more paying audience members). It also seems to me that the lower down the scale we go, then the more vernacular the language that is used. In pieces of high performance, the language is more literary, more carefully considered and constructed, more conscious of its own techniques, devices, poetic flourishes and cleverness.
But there is a potential problem here (and one that I haven't resolved). If the use of vernacular language is a defining feature of 'traditional storytelling', then this means that the storytelling of professionals is by and large less traditional than that of the general public, and the more overtly performative a storyteller becomes, then the less traditional s/he becomes! Do you see what I mean?
Do we rather need to say that vernacular language is a hallmark of an oral tradition and that most modern professional storytelling is a mixture of oral and literary traditions? It may be that we're getting confused by also using the term 'traditional' to mean 'purely oral'. It could all be traditional - just a different balance of traditions!