"If all folk musicians and all folk events were exempted from involvement with PRS, one major result would be that whatever earnings are currently accruing to folk PRS members would stop."

Yes, Anne - if we only we could tell them what the word 'folk' actually meant! That's one of the reasons why I always say we should all try to be aware of the difference between copyright and non-copyright material and know which we're playing. The business of having both lumped together and jumbled up in our minds is very unhelpful when it comes to issues like trying to persuade PRS that they're charging too much for the wrong material, for example.

Perhaps we need a third category. Music which is technically copyright (see Richard's very good point above) but which has been let loose, so to speak, but without formal abandonment of copyright. Could it be free to perform when no money's changing hands, but chargeable when it is, or something? That would then cover 99% of session tunes, and a fair number of popular non-trad songs. Maybe 'In public use?'

But finding a definition and a system of accounting which the beaks would accept... Now there's the rub!