Al, thanks for your comments.
You're welcome, and thanks for your post.
I must say that I find Schnittke's music problematic, but in a way which somehow makes me want to understand more about what lies behind it. In general I have little sympathy with the idea of "polystylism", but I think that Schnittke's music is disturbing on a deeper level than this: it seems sometimes to consist of the most extravagantly maudlin gestures and references, but sometimes I also have the impression that this feature is a surface beneath which a vast equivocation and ambiguity is lurking.
Exactly right.
You mention Shostakovich: Interesting how this, supposedly straightforwardly "manipulative", composer completely subverts the idea of the "triumphant finale" in the finale of the 5th symphony. At first I did not realize it, and it took me a few listens to "get" it and only after some exposure to Mahler (at the time I was new to classical music, however). I don't claim that Schnittke works the same way as this music though.