Regarding the question of whether it is 'useful' to use the concept of mediation to refer to interpretations of songs by singers:

Could we consider the possibility that it might actually be a positive thing? I ask this because some people complain that terms like 'tradition bearers' in effect factor out the individual creativity of the singers. I think that his phrase was one of Lloyd's when he was in Sharpian mode as opposed to Marxist mode.

Moreover, terms like 'song carriers' and 'tradition bearers' distract attention from the fact that if the song is old it will have been sung in a variety of very different historical contexts. You do not have to believe in a Marxist or Marxian theory of history as class struggle to agree that this is the case. The song is likely to have meant something different to each of the people who sang it or even discussed it. Changes made to the song may reflect the particular time they were made, or even more personally the attitudes, opinions and values of those making the change.

I think the same applies to the music chosen, as some tunes have acquired particular connotations.