BH:

The event I'm talking about is 'The Bury St Edmunds OXJAM folk weekend ' and that's how I've billed it, so if I adopt your policy, then I would have to re-brand it as 'The Bury St Edmunds OXJAM mix of traditional song, new songs in that style, contempory songs and folk/rock weekend'

My answer's the same, which is that it's all about the content, not the labelling. If you care about 'folk' being used to denote a certain kind of music, then - if you've got anything to do with an event that's labelled 'folk' - you'll try to maximise the amount of that kind of music that gets played at the event. And if you don't, you won't.