[Theowne]

Judging from some of those pieces, artistry is the last thing on the composers' minds.

Well, I know many people who listen to a particularly loud Rachmaninoff piece and say the same thing, many of Debussy's contemporaries found his music unbearably dissonant and artistically vapid as well. I don't particularly like atonal music myself, but I don't doubt that they believe their music is artistic.

What would you say is the defining aspect of 'classical music'?

Good question. When I hear the term, what I imagine is a lineage of Western art music which progressively builds on previous traditions. Serial contemporary music, to some extent, can be seen as a part of that line, building on the mileu of composers like Bartok or even Debussy (even if not many like the result) so some people, not all, would classify it as the modern "classical music".

If film scores are performed independently as 'art' in a 'concert' setting, would it suddenly become classical music?

Many film scores are already performed in concert settings, though usually as "pops" concerts. If you mean if they were composed for concert settings, then that would certainly have a stronger case, but then it isn't a film score. I suppose it's hard to explain, or rather, I'm not good at explaining it.