Rather than choosing the supreme works from different schools, "organized
according to the reassuring development of a genealogical tree", let me
suggest adopting a different means of categorization put forth by Jean
Clay, author of one of my favorite books on modern painting:

Color:  "It frees itself from its ancient descriptive function....to become
henceforth merely itself."

Distortion:  "The expressive distortion of Classical canons reveal
spacings, shapeless areas in which the pictorial substance begins to
create a specific atmosphere...."

The Pulverized Object:  "The object is decomposed into a puzzle of
fragments...linear perspective is abolished."

Frontality:  "...internal logic dictates form.  Step by step surface
organization gains over representational depth."

The Real Object:  "The real object is introduced into the composition...
either inscribed into the coherence, or used to explode the work under its
imported presence."

Now, I fully realize that I'm borrowing vocabulary that has particular
meaning when applied to the visual arts, but it's still fun to use these
categorizations for music.  With these categorizations, one can link
seemingly unrelated composers in new and surprising ways.  By using this
approach, It is much easier to see the roots of *all* 20th Century music,
no matter how forbidding, in the earlier centuries.

My own comparisons to come.  Have fun!

John Smyth