"Never was anything as incoherent, shrill, chaotic and ear-splitting produced in music. The most piercing dissonances clash in a really atrocious harmony, and a few puny ideas only increase the disagreeable and deafening effect."

 This remark aptly characterizes the reaction of many listeners to the music of Arnold Schoenberg. But this particular criticism comes from the pen of the dramatist August von Kotzebue, writing in 1806 about the overture to Beethoven's opera Fidelio.

Both Beethoven and Schoenberg stirred controversy because of the way they altered the language and extended the expressive range of music. Beethoven, of course, has stood as a cultural icon for more than a century, but that didn't happen overnight. His most challenging works did not become popular until well into the twentieth century and, significantly, after the invention of the phonograph, which made repeated listening possible.

Like Beethoven, Schoenberg worked in a constantly changing and evolving musical style that acknowledged tradition while simultaneously lighting out for new territory. This is true of the three different musical styles through which Schoenberg's music evolved. He began in the late-Romantic manner—music charged with shifting chromatic harmonies—that was pervasive in his youth. People who enjoy the music of Brahms ought to love Schoenberg's Verklaerte Nacht, and they usually do, once they get past the fact that they are listening to a piece by Schoenberg.

Schoenberg later pushed those unstable harmonies until they no longer had a tonal basis. He did this in part because in his view it was the next inevitable step in the historical development of music, and he felt he was a man of destiny; he also did it because he needed to in order to express what he was compelled to express.

Finally, he developed the 12-tone technique as a means of bringing a new system of order to nontonal music and stabilizing it. In all three styles, Schoenberg operated at an awe-inspiring level of technical mastery. As his career progressed, his music became more condensed, more violent in its contrasts, and therefore more difficult to follow.

But the real issue for any piece of music is not how it is made, but what it has to say. If Schoenberg hadn't existed, it would have been necessary to invent him, and not because of the 12-tone system, the seeds of which appear in Mozart. What makes Schoenberg's music essential is that he precisely delineated recognizable and sometimes disquieting emotional states that music had not recorded before. Some of his work remains disturbing not because it is incoherent, shrill, and ear-splitting, but because it unflinchingly faces difficult truths.