Part IV of an occasional series.
If you went to music school twenty-five years ago, your history professors portrayed mid-century serial music as the Great Experiment - nothing less than the logical culmination of a mounting trend towards complexity which can be traced back to the time of Gregorian chant. If you go to music school now, your history professors are probably somewhat embarrassed by mid-century serial music - they portray it as a historical blip, motivated largely by peer pressure, which is historically interesting but best forgotten. Implicit in both assumptions is the idea that there is a Correct Way to write music - it's just that one side thinks that Milton Babbitt is the standard-bearer, and the other has their money on David del Tredici.
I've gone into almost painful detail previously on why I don't like either model. What I have to offer instead is hardly an encyclopedic worldview, but a few observations which I've found useful in dealing with the mess of a century we just came out of. This first post borrows the scientific term "dynamic equilibrium", which most correctly refers to a sort of stalemate situation which is reached by most chemical reactions. Individual molecules in the reaction continue to collide with each other to form new compounds, but the overall situation has stabilized such that the proportions of the different substances in the reaction remain the same.
The term "dynamic equilibrium" works for my purposes, but it should be noted that the term "stochastic process" is possibly even more apt for the situation I'm describing; a stochastic process is a semi-random one in which the overall tendency of the process (for example, the movement of gas molecules in a closed container) is predictable, but the behaviour of individual elements (for example, the individual gas molecules) is too complex and interdependent to develop fully. I've avoided using the term "stochastic" because, of course, Iannis Xenakis has already applied it to music to describe a specific compositional approach.
My contention is that individual composers exist in a state very similar to that of dynamic equilibrium. General, vague trends and compositional fads can be discerned if you look from far away and squint a little, and these trends fairly a number of individual composers (usually, the ones that aren't very good). However, if you look closer you notice that the style characteristics of the other composers vary widely: in terms of complexity, in terms of motivic and contrapuntal activity, in terms of harmonic language, and in any number of other ways. Until finally you see composers that seem to belong to another time and place entirely than their own (Ives, Gesualdo, Rubbra)
The other similarity to chemistry, of course, is the fact that the fluctuations in the process are caused by interactions between individuals (whether molecules, in the chemistry version, or composers, in my version). Thus, the extent to which an individual composer may or may not reflect the overall Zeitgeist is determined not only by his own intentions, but by his interactions with others, whether they try to push him in one direction (cf. Pierre Boulez) or another (Josef Stalin). The idea of a bunch of composers flying around in midair and bouncing off each other (Classical Music Pinball!!) is perhaps amusing, but it also reflects several common verbal tropes (cf. "Let me bounce this idea off you").
Notice that accepting this model does not necessarily invalidate the old generalizations about music history ("Everyone wrote neoclassical music until mid-1953, when they switched to serialism before moving to neoromanticism on August 9th, 1976, except for those two months in 1982 when everyone wrote spectral music") - however, it makes it clearer that these reflect general trends only. It also means that one of the hoary old tropes of music journalism, in which every composer who writes differently from the Statistically Average Composer is treated as a Card-Carrying Rebel (cf. Andrew Ager) can hopefully be buried; composing differently from your colleagues is perfectly normal and makes for a much more interesting contemporary music scene. Finally, it reflects my own belief that the spread of compositional trends is partly random: there's no Historically Inevitable reason why Schoenberg's twelve-tone method became the rule rather than that of Hauer, Roslavets, or, heck, Richard Yardumian.
Messiaen provides a ready case-study, and not only because it's his birthday. His own tendency (as influenced by Debussy, Dupré and his other predecessors, as well as by his idiosyncratic compositional interests) was toward a modal harmonic language with idiosyncratic rhythms and unique melodic and cadential patterns. Flying around in the pinball machine, however, he hits Pierre Boulez (ouch!) and goes careening off in a different direction, this time one in keeping with the prevailing avant-garde aesthetic. A number of other, smaller collisions eventually return him to a similar course to his original one, and he is once again a Conservative Composer. The overall system is in equilibrium but Messiaen himself has gone through a number of changes. (It's also interesting to note that one can read a state of dynamic equilibrium into Messiaen's works themselves: in the Livre du Saint-Sacrement, for example, compare "Prière après Communion" with "Les ténèbres".)
If you've been paying close attention, you've probably noticed that I've taken a great deal of time to make the point that composers are influenced by their own personal stylistic tendencies, by other individuals, and by broader social and musical trends. Which should hopefully not be extraordinarly controversial, but you never know. This is not intended to be an all-encompassing system (in fact, that would be missing the point), but rather to restore some of the sense of individuality to the way that we talk about music.