I would like to start off by paraphrasing Charles Wuorinen, in a lecture at June in Buffalo, 2006:
“Since the definitive collapse of tonality in 1909, art music has seen a lot of flailing around which hasn’t amounted to much.”
Wuorinen is a staunch supporter of post-tonal music, the serial method in particular. He even wrote a book about his techniques, titled (appropriately enough) Simple Composition.
What happened in 1909? Scholars point to Arnold Schoenberg, the Austrian composer. Around that time, Schoenberg composed several works which eschewed tonal centers. Perhaps the first was Drei Klavierstücke, Op. 11 (see the video below for the score of Mvt. I and a performance by Glenn Gould). Schoenberg’s new style was quickly dubbed “atonal,” which the composer found annoying because it means “without tones.”
When you listen with fresh ears, you can hear the expressiveness which this style allows. Without the constraints of traditional harmony, the composer can create new melodies and harmonies that can better express his sometimes extreme emotions. Unfortunately, over the past century not enough people have listened with fresh ears; they have listened with traditional ears.
In my experience, some of the most traditionally-minded ears belong to trained musicians. In many music schools, post-tonal music is glossed over at the end of music history class. It is described in terms of “madness” and “cats walking on the piano.” Essentially, music teachers are indoctrinating music students in the notion that “after 1909, music went crazy and was no longer worth listening to.”
Rather than writing crazy music for the purpose of being crazy, Schoenberg and Varése simply sought emancipation – of dissonance, of all sounds. Atonal or post-tonal is not by definition “ugly,” just liberated from the constraints of tonal harmony. Even if classical music went a bit crazy, is this a bad thing? Literature went crazy (Joyce? Burroughs?) as did visual art (Picasso? Duchamp?). Somehow art music was left behind in a vault. New music was being created, but it was doomed before it was released.
Obviously there is good and bad post-tonal music. Not all of it deserves to survive, just as not all Romantic or Baroque music deserves to survive. However, a whole movement has largely been discarded because of a misunderstanding.
The misunderstanding seems to be that modern composers wrote music with the express purpose of annoying the audience. This could not be further from the truth. Modern composers only sought the freedom to write in whatever way would best express their ideas. This could be through traditional tonal harmony, through serialism, chance, minimalism, post-modern collage, et cetera…
The theme of the Post-Tonal Century is not dissonance. It is liberty.