Phil, I'll just repeat what I said earlier, form/idiom/style all have the same meaning in the context of this debate.

So help me out here with a practical example, I'm in the process of organising a weekend event that will contain a variety of music, from traditional songs, new songs in a traditional style, other modern songs in a more contemporary style and even some of that dreadful folk/rock.

How do I describe this event? Should the advertising read 'a weekend of folk music and other music using folk forms'

Gets a bit long winded, so I'd be interested to hear your suggestions