Extremely broadly speaking, Western classical music can be divided into three large stylistic and chronological chunks. The first of these, which we now call "early music," encompasses the medieval and Renaissance periods (ca. 500-1600 CE), during which the modal system held sway. In this system, composers chose notes from a set of groupings called modes, which did not necessarily mirror one another in the pattern of intervals between their constituent tones, thereby giving each mode its own distinct character. The chief means of creating complexity was the weaving together of multiple, in some cases many, independent melodic lines; harmony was of course an important part of the character of the resulting music, but it was created as a byproduct of the intricate counterpoint rather than designed as a key structural element.
The emergence of the Baroque style around 1600 marks a turning point and the beginning of an era now known as the common-practice period, which continued through the Classical and Romantic styles of the 18th and 19th centuries and encompasses the majority of the standard repertoire that remains so beloved today. The common practices that tied together the music of this era were many, but the most important was the diatonic, or major-minor, system of tonality, familiar to anyone who has taken a music lesson. In the diatonic system, the harmonic structure is based on seven-note scales—which can begin on any note and then follow set patterns of intervals from one degree, or step, of the scale to the next, depending on whether they are major or minor—and on the fundamental three-note chord structure known as the triad. These triad-based harmonies are then used in specific progressions and combinations according to a detailed system of relationships between the degrees of the scale. The purpose and power of the diatonic system is that it establishes a clear and subconscious set of expectations in the ear and the brain, which can be fulfilled, frustrated, and otherwise manipulated by the composer to create almost any desired effect.
As the Romantic period progressed, however, some composers increasingly chafed under the rules and traditions of the diatonic system and began to push its boundaries in order to achieve even more freedom of expression. By the mid to late 1800s, composers such as Wagner, Liszt, and Debussy were writing unabashedly chromatic and harmonically promiscuous music that only loosely and intermittently adhered to the tenets of diatonicism. Finally, in the first decade of the 20th century, the tonal monopoly of the common-practice period came crashing down. Several influential composers—most importantly Arnold Schoenberg, Anton Webern, and Alban Berg, collectively known as the Second Viennese School—abandoned diatonic harmony altogether and ushered in the third overarching chronological period, an era that stretches from the fin de siècle to the present day. This era, which as yet has no useful name (having received mostly meaningless, relativistic labels such as modern and contemporary), is defined by its very lack of definition-its constant stylistic splintering and consequent absence of a dominant methodology.
This afternoon's program is a portrait of the three revolutionary thinker-composers of the Second Viennese School, and through it we hear part of their pioneering search for new musical worlds—both collectively and individually—as they journeyed into the blank areas of the musical map. From the capricious, unfettered roaming of free atonality, in which there are truly no rules, to the puzzle-box music of 12-tone technique and serialism, whose rules can be far more strict than diatonic tonality had ever been, the innovations of these three men rebooted Western art music. Everything that has been written since has had to reckon with their legacy and influence in some way; it is a testament to how much the Second Viennese School accomplished that one of the most controversial statements a composer could make for much of the 20th century was to carry on writing music that didn't show its influence at all.