Actually M. Ted raises a good point - each type of music will tend to bring in its own crowd. It is interetsing to note this at the folk club I'm involved with. We can have a packed house for a group like Maza Meze - a toronto group getting good press and playing a Middle Eastern/Greek mix (Masa and Meze meaning appetisers in both languages) but I can usually only recognise about 4 people who would be there on another night where it may be more British. Likewise with Bulgarian music etc.
We tend to get different crowds for the different types of music - the Irish crowd will come for the Irish stuff, English trad will have a diferent crowd to that, singer-songwriter different to that.
Because of our audiences and getting the word out, we have tended to stay in the the direction which allows us to get an audience out- attempts to broaden the horizon have not been that successful (with some exceptions). A latin group would do much better in a different venue and thankfully they exist.
Rana