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This imperfect union was foisted on generations of musicians in France’s conservatories, the most prestigious of which Debussy attended at the ripe age of 10. Blessed with an extraordinary ear, he had an intuitive grasp of sound that outpaced his assimilation of theory. The result was a young student who bewildered his instructors. While evaluating a composition exercise, one commented: “Obviously, all this is hardly orthodox, but it’s very ingenious.” Another, though impressed with Debussy’s “initiative and verve,” dismissed him as “a bit of a fantasist.” School assessors, less equivocal, accused Debussy of being “preoccupied solely with creating the strange, the bizarre, the incomprehensible, the unperformable.”

For Debussy, these were the first of many critics. The respect of the Parisian establishment was long in coming—an appreciation deferred by his musical heterodoxy, as well as a series of romantic indiscretions. (His tendency to mock mainstream artists didn’t help, either.) Only decades after his death was he lauded as the pioneering genius he’s considered today. Walsh—who previously authored a biography of Debussy’s younger contemporary, Igor Stravinsky—explores that genius with erudition and style. Tracing the evolution of Debussy’s methods and imagination, he also probes the toll the composer’s labors took on himself and those around him. The fantasist experienced his share of worldly trials.

“It seems to me that music can make itself more human, more lived, that one can excavate and refine the means of expression”: As a recent conservatory graduate in his early 20s, Debussy voiced this hope before quite knowing how to realize it. But he was convinced from very early on that the musical grammar he learned in school—its thematic structures and harmonic rules—stood in the way. So he set out to create his own grammar: a new system of musical language that preserved the stabilizing virtues of classical theory while escaping its aesthetic limitations.