“One feels,” he writes, “that in the midst of an era ever more imbued with memory, to forget becomes so urgent.” It could be Sartre speaking, but it’s Boulez trying to cut a clean path through the overgrown thicket of too much tradition, thoughtless habit and unquestioning routine. When he laments that “we wilt under the weight of models,” he expresses the burden that we composers today must endure, living and working in the shadow of past masterpieces and the culture of “greatness.” But memory, both collective and individual, is for him a double-edged sword, capable of stimulating and informing the creative act, while also threatening to corrupt it.

Boulez believed in the absolute value of the work of art. Anything not contained in the notes on the page he dismisses as “documentary evidence,” be it performance tradition, anecdotal history, biographical gloss or even recordings. The “text” for him is the notated score, the only true “mentally reliable resource, safe from any other form of dissemination.”

So issues of identity, society, politics and environment that are dominant forces in the creation of new works today play no role in “Music Lessons.” In judging an artwork, Boulez is adamantly indifferent to its back story, its sociopolitical implications or its creator’s personal narrative. This skepticism and his Apollonian sense of exclusivity can seem old-fashioned, and were he alive in 2019 — as the conventional canon is being probed and re-examined — he might well be called upon to defend his position.

A glance at the book’s index reveals the areas that instead dominate Boulez’s concerns. Most of the entries border on what might be called musical metaphysics: articulation, chance, composition, continuity, deduction, duration, form, idea, language, material, notation, perception, rhythm, structure, succession, theme, timbre, tradition, variation. If this seems dry, it isn’t. Boulez inevitably has something observant to say, in prose that’s refreshingly free of academic jargon. That’s a good thing, because his theses often demand patience and effort to unpack.

But be warned: His universe of valued music is a severely limited one. A reader who cannot immediately identify with a handful of canonical names — Wagner, Debussy, Schoenberg, Stravinsky, Berg, Webern, Bartok and, of course, Boulez — may feel left out of the conversation. And when it comes to new music, although he is too subtle to be prescriptive, the elephant in the room is atonality: Tonal harmony has, for Boulez, been essentially exhausted of its potential over a century ago.

I couldn’t help but wonder how a highly intelligent and aware musician living in the latter half of the 20th century, and the opening of the 21st, could write a 650-page book that completely ignores popular music, the defining cultural phenomenon of our time. Perhaps for Boulez, popular music was a social discourse rather than a musical one, its essential characteristics being too primitive to discuss as art? About jazz he is only marginally more conscious than Adorno, who could never get beyond its association with commerce to appreciate it as an art. And of Minimalism, surely one of the most important stylistic watersheds of 20th-century music, Boulez makes only a passing reference to its “simple phasing or superimposing different periodicities, of which one quickly wearies as soon as one senses how they function.” Really?