Going back to my original contention that only type 3 is a folk club: what does the word 'club' mean? Type 3, which one would traditionally assume to have a regular audience, can be argued to consist of a number of people 'clubbing together' to book guest performers. A session is a group of people, not necessarily regulars, getting together to play, as a joint activity. You don't pay to join in. How is it a club?
John Kelly.