Thanks, Jeremy, that was the sort of answer I was looking for.  Also thanks
to Steve Schwartz for the list of suggested listening, and the rest of you
who responded to my initial query.  It sounds like I was not so far off the
mark with these Boulez piano sonatas, but that there is much more out there
that might be better, more interesting, more "listenable".  Thanks.

Sylvia Wolfe