What is wide, the gap or the knowledge?
Oops, John, sorry for the ambiguity there. Well, you could certainly show most of us a thing or two about putting a quiz together, that's for sure.
The way that some new music festivals are publicised is distinctly unhelpful to anyone who is not closely involved in that world; perhaps, dare I say it, even somewhat threatening, since what Richard describes as "desperate acts of defence against a hostile cultural environment" can, to a potentially interested outsider, appear almost aggressive, defensive and hostile themselves
That's true, Roslyn, but I'm also often irked by a complimentary tendency wherein the music is presented in a patronising and hyperbolic way like the SPNM's "Riot" concert (qv) which as riots go wouldn't ruffle anyone's blue rinse. I think the answer is (as indeed it used to be) not to hive contemporary composition off into a ghetto but to present it unapologetically in the context of its cultural environment, as in the Proms, or indeed the recital programming of musicians like Ian when he has the opportunity.
I hate to mention the word 'Stockhausen' again, Richard, but you do seem to be agreeing with me ...
I thought we'd sort of agreed that we actually agree on such matters, hadn't we? Now that I've let go of the wrong end of the proverbial stick, that is.

all sorts of rather trashy (but very popular) pop song-writers
Like Evan Parker, you mean? Seriously, though, I think it would be interesting to explore what kind of biodiversity goes under the name of "composer". I'm frequently brought up short by the fact that there are people out there (thousands!) who have the same "job description" as I do but whose activities I don't recognise as having anything in common with my own apart from resulting in some kind of audible stuff. Maybe the word "composer" is where the problem lies.
What would be the basis for excluding them?
I think one should be looking for reasons to
include people, not to exclude them. No selection is going in the end to embody an objective decision-making procedure - choosing a group of interviewees is after all a process of "com-position" which says much about the interviewer and his/her priorities. What we're all talking about here is how each one of us might approach the issue. My model, by the way, would be the novelist Alan Burns' book of interviews with his contemporaries (published in 1981, but containing material from some time earlier like the interview with BS Johnson),
The Imagination on Trial.