Books on Composition (old item revisited)

Alex Ross has put up a swell quote from Charles Seeger's Dissonant Counterpoint. Seeger's essay has been an inspiration throughout my life as a composer and was one of the items on a list of books on composition, first posted here on February 12th:

These are a few of the books more-or-less directly about composition to which I have returned frequently over the years:

Cowell, Henry, New Musical Resources
De la Motte, Diether, Kontrapunkt (This, unfortunately, has not yet been translated into English).
Erickson, Robert, The Structure of Music, A Listener's Guide
(Erickson's later book, Sound Structure in Music, mostly about timbre, is also interesting, but for whatever reasons, I have never returned to it)
Harrison, Lou, Lou Harrison's Music Primer
Kühn, Clemens, Formenlehre der Musik (needs to be translated)
Morley, Thomas, A Plaine and Easy Introduction to Practical Music
Mozart, W.A., Attwood-Studien (The harmony and counterpoint notebooks of Mozart's student Thomas Attwood)
Seeger, Charles, Harmony (Sadly, very difficult to find!)
Seeger, Charles, Dissonant Counterpoint (article)

These come from the visual arts, and say nothing explicit about musical composition, let alone tuning, but they are so rich in ideas that I can't imagine not having them near my desk:

Klee, Paul, Pedagogical Sketchbook
Weschler, Lawrence, Seeing is Forgetting the Name of the Thing One
Sees: A Life of Contemporary Artist Robert Irwin

I'm not alone among composers in having found this valuable:

Thompson, D'arcy, On Growth and Form

These are more recent additions to my library, so have not yet faced
the test of time, but are certainly worth a look:

Andriessen/Schönberger, The Apollonian Clockwork: On Stravinsky
Ashley, Robert (ed.), Music with Roots in the Aether
Lucier, Alvin, Reflections/Reflektionen
Tenzer, Michael, Gamelan Gong Kebyar: The Art of Twentieth Century Balinese Music (a very important book on ensemble composition).
Wolff, Christian, Cues/Hinweise

I continue to be impressed by John Cage's contribution to the Hoover/Cage Virgil Thomson; Cage was a gifted writer about practical musical technique.

One of my students recommends this so strongly that I include it here despite my own reservations:

Mathieu, W.A., The Harmonic Experience

We still need a contemporary volume to replace Helmholz's The Sensations of Tone. William Sethares' Tuning, Timbre, Spectrum, Scale is an important book. Richard Parncutt's Harmony: A Psychoacoustical Approach is one of the more interesting pieces of scholarship in the field. It's out of print, but the publisher has admirably allowed for free downloads, via:

http://www-gewi.uni-graz.at/staff/parncutt/hapa.html

Addendum, December 2006:

Here are two books that I have recently found to be very useful:

Shere, Charles: Thinking Sound Music: The Life and Work of Robert Erickson
Scherchen, Hermann: Lehrbuch des Dirigierens