Karol Berger's book Bach's Cycle, Mozart's Arrow sets as its task the origins of musical modernity, specifically from the perspective of musical time. Berger carefully distinguishes modernity from modern music, where modernity is a fissure in a continuous historical lineage, generally located around the Industrial Revolution (with the French and American revolutions as the political counterparts). In pre-modern times, time was viewed as a cycle (e.g., of the sun and the seasons). By the end of the 18th century, time was viewed as progressive, a linear history moving from the past toward the future. Berger chooses Bach and Mozart as musical illustrations of these two perspectives, and Augustine and Jean-Jacques Rousseau for philosophical background.
His chapters on Bach deal primarily with the St. Matthew Passion (which it has been a pleasure to hear again), with a short interlude on the first fugue from the WTC. The most illuminating section on Bach was on the fugue, which points out that the events in the fugue do not depend on one another in any meaningful way. Given the subject of a fugue, a certain number of "demonstrations" of the way the subject(s) may be harmonized and combined, each demonstration being independent of all the others. The demonstrations are essentially in an unordered set. Bach of course does combine them in a meaningful way according to a tonal plan, but in Berger's estimation, this combination comes later, and is of lesser importance than the demonstrations themselves.
I was much less moved by his discussion of the Passion, where he shows how Bach musically represents the Christian belief that our finite human time is enmeshed in the infinite time of God. While I don't doubt that this was indeed Bach's intent, the Christian story was considerably more real in Bach's time than it is in ours, where it has become more metaphorical (this is part of the transition to modernity that is the overall subject of the book). I don't believe one needs to be a devout Christian, versed in the arcane details of 18th century theology, to appreciate this magnificant work.
Undeniably, by the time of the Viennese classics, a listener was certainly expected to remember various events that occurred in the course of a piece. The classic sonata form, with two themes, a development and a recapitulation, all on a fairly standard tonal plan, makes little sense without some kind of short term memory to understand the structure of the piece. Berger demonstrates musical linearity with detailed examples from Mozart and Beethoven, but in both cases already showing how the conventions of the sonata form become expectations to be subverted.
A long interlude in the center of the book describes in some detail the philosophical changes that underpin Berger's arguments. Both the theological arguments behind the eternal time that precedes and follows the insignificant human time scale, as well as a summary of Rousseau's philosophical positions on our rational self-determination, are presented in some detail. Berger's intent is to show the philosophical changes that were current during the late 18th century, and which informed both the composers and listeners. If the arguments seem a bit esoteric and irrelevant today, an awareness certainly can inform contemporary interpretations of the music.
Granted, the classical concert repertoire is often too heavily invested in the Viennese classics that form the primary focus of this work. But when Berger says that "the Viennese classics have shaped our musical expectations and values to such an extent that we expect these values to inform any music we encounter," well, I'm sorry, but Berger needs to get out more. Discontinuity and various kinds of nonlinearity have been part of classical music since Schoenberg and Stravinsky — are there corresponding changes in our views on time? What perspective change do we need to appreciate a mobile form work like Cage's Atlas Eclipticalis, where the linearity is subverted from one performance to the next? Unfortunately, Berger's steadfast refusal to consider modern music (as opposed to modernity in general) makes the book somewhat less interesting to the general reader.