I noticed something interesting as I was giving Bartok's 4th String Quartet
another listening.  It is structured like Hebrew poetry, very similar to
the chiastic structures of the Psalms of David and the Book of Job.

The weight of the quartet is found in the middle movement, the Lento.  The
fourth movement corresponds and repeats the ideas in the second.  The fifth
movement likewise corresponds and repeats the ideas in the first.  Although
you hear the movements in succession (just as you would read the strophes
of a psalm), the main idea is found in the center and the developments of
the theme fan outward.  The chiastic structure of the fourth quartet would
look something like this:

   1. Allegro
   2. Prestissimo
   3. Lento
   4. Pizzicato
   5. Allegro molto

I doubt Bartok had the chiastic structure of the Psalms in mind when he
wrote this particular quartet (then again, maybe he did-- I don't know),
but there must be some sort of musical term or description for this type of
structure or plan.  Hebrew poetry is full of parallelisms and you can see
the likeness from what I charted above.

For all the advanced techniques and variety of style in these quartets,
they still sound like finger nails scrapping a chalk board. . . but they
are slowly growing on me.

Mark