On December 1, 1900, at an intimate concert hall in Vienna, a respected local baritone gave the premiere of some early songs for voice and piano by Arnold Schoenberg. Today this music, though written in an elusive harmonic language, comes across as exuding hyper-Wagnerian richness and Brahmsian expressive depth. But the audience in Vienna broke into shouts, laughter, and jeers. From that day on, as Schoenberg ruefully recalled two decades later, “the scandal has never ceased.” The author Harvey Sachs relates this story, and describes the songs sensitively, in his new book, Schoenberg: Why He Matters. As Sachs makes clear, the “scandal” only got worse. In 1908, Schoenberg premiered the Second String Quartet, his boldest step thus far toward breaking the tethers of tonality—the musical language of major and minor scales and keys that had been around for centuries. Plush with wayward harmonies and arching vocal lines, the music is dark, moody, and entrancing. But most of the audience heard only piercing dissonance and rambling stretches of ugly sounds. One reviewer deemed the piece not …