The music in one’s head and the music on the page are examples of the two cerebral hemispheres, and they really are entirely different animals. The first is the True Inspiration and the latter is how the True Inspiration can be translated into something musicians can actually play and people can actually hear. Left brain, right brain. Maybe they’ll take a picnic together sometime.Ah, dualism; that left-brain/right-brain caricature is a pernicious one, isn't it? Good and evil, communism and capitalism, atonality and tonality, Dick York and Dick Sargent—I blame it all on bilateral symmetry. If we had three arms, we'd probably think in terms of light, dark, and, say, crepuscular.
But maybe the whole notion of True Inspiration gets at another division: systematic and non-systematic composition. Again, a dualist caricature—composers don't pitch a tent in one camp or another, but take up residence somewhere along a continuum. But where you end up depends on your own relationship to True Inspiration.
Shapiro is obviously a composer for whom inspiration comes first: it's the initial idea, the spark, that drives the actual work of composition. This is, I imagine, how most non-artists imagine artists working. But my own experience is different: every True Inspiration moment I've ever had has invariably happened in the middle of a work session, after I've already been plugging away at the material for a couple of hours. I have no clue if an idea is an inspired one until I've tinkered with it for a while, and then it opens up and I can see where it's leading, what it can become, how it can shape a musical paragraph or movement. Or that it can't, in which case it goes in the trash, and I start from scratch the next time.
As such, I have a natural sympathy for compositional systems—it's how I investigate the possibilities of an idea. Mash it into a chord or stretch it into a melody and see how it sounds. Run an interval vector on the set and start transposing it around. Collect up the remaining pitches to form this or that aggregate and tinker with the juxtaposition. Or a particular rhythm: how's it work in augmentation? Diminution? Canon? Layer it over various phrase lengths—does the pattern shake out regularly? There's the old stand-bys: inversion, retrograde, combinatoriality (be the context tonal or atonal).
For me, once an idea opens up a possible landscape, a lot of the systematic determinism falls away—I live probably just left-of-center on a left-to-right systematic/non-systematic spectrum. I have favorite composers from all over the map—Poulenc was non-systematic and proud of it, as opposed to Stockhausen or Boulez, happily ensconced deep on the other side: the system itself is the inspiration, the music its realization in sound. Which, in a full circle sort of way, is not that far from Shapiro's description.
Thomas Edison perfected the light bulb by methodically testing some 6,000 different filaments; Leo Szilard suddenly glimpsed the entire mechanism of a nuclear chain reaction as he crossed a London street. Of course, Szilard's vision required a Manhattan Project to reach fruition. Edison's old saw—10% inspiration, 90% perspiration, or some comparable ratio—still holds, but some of us have to sweat first before the muse deigns to put in an appearance.
Update (2/13): ACD demurs:
[B]y the end of our reading he’d set our teeth to grinding, for what he described with some affection is a virtual definition of precisely what's wrong with most so-called New Music; a veritable instruction manual of how NOT to go about the making of the thing.Let me be clear: I'm not saying this is how things should be done, but it is how I personally do things. As for affection, I would hazard a guess that I do have affection for a lot of music that ACD doesn't care for, but my affection has nothing to do with its construction, but rather its effect in performance. My point was that there's a lot of different ways to realize that final effect, and that the spark of inspiration can happen in a lot of different places during the work of composing. I would love it if entire pieces or even entire well-formed musical ideas came to me out of the blue while I was sitting on park benches, but for whatever reason—temperament, brain chemistry, undiagnosed ADHD—they don't. So I do what I can to get the muse in the mood, as it were.
It's worth pointing out that I was fascinated with systematic manipulations of musical material long before I heard of set theory or total serialism. I learned augmentation and diminution from the d-sharp-minor fugue in Book I of the WTC; I learned inversion from Rachmaninoff's Paganini Variations—the old stand-bys are old indeed. For an exceptionally fine example of consciously, systematically manipulated materials, look no further than Sondheim's Sweeney Todd; I spent the better part of a semester in grad school happily tracing all the mutations of the Dies irae theme in that score. And after all, music itself is already a highly organized system—that the end results are so wonderfully varied is as much a testament to the power of that system as it is to the power of inspiration.
Update II (2/18): Marc Geelhoed has sharp observations from a more performer-centric perspective. He also references the "divine afflatus," which is as good an excuse as any for linking to what, for a few months at least, was my favorite mural in all of Boston.