Don't forget George Crumb's Macrocosmos (sp?) for piano. One of the
movements the music is arranged in the shape of the greek letter theta
(basically a circle, with a horizontal line bisecting it.  After playing
the top half of the page (including the horizontal line), the page is
turned upside down and played (including the horizontal lines, now
backwards and inverted), concluding with the bottom half of the circle
(now at the "top").  The Palindromic sequence is based on the "Dies
Irae" and works surprisingly well.

Gary Evoniuk
Durham, NC