Guest,

'There is of course still the question of how anybody working now can add to the canon of material. Assuming that they are working identifiably within the traditional style.'

The only people who can decide whether something is or is not added to the folk 'canon' are the 'folk' themselves, whoever they are, certainly not the song writer or you or me. Where there is a strong lively oral tradition (soccer chants, playground songs) material is being added all the time but it is filtered subconsciously by the folk involved first.

If you mean added to the folk-scene canon then anything rejected by the folk police is liable to make it.