Measure by Measure will return on July 6. In the meantime, here is a second look at Sudip Bose’s essay, from our Spring 2015 issue, on Debussy’s playful, devilish, harmonically inventive études.

By the time he began composing his monumental set of 12 piano etudes, 100 years ago, Claude Debussy could look back on his body of work and know that he had attained a place among the greats. And yet, at the outset of the summer of 1915, there was little indication that he had any more masterpieces in him.

Increasingly melancholy and reclusive in the last decade or so of his life, the composer only rarely ventured beyond his home overlooking the broad Avenue du Bois de Boulogne, in Paris’s 16th arrondissement. Relations with his second wife, Emma, had long been strained, and he suffered almost constantly from hemorrhages and hemorrhoids, symptoms of the rectal cancer that had yet to be diagnosed. Always something of a penniless bohemian with wildly expensive tastes, he had been sinking even further into debt. He was also finding it difficult to compose—burdened not only by the weight of his past success but also by concerns of his place in a musical world upended by the emergence of Igor Stravinsky. Germany’s declaration of war on France in August 1914 brought greater hardships. Seething with anger, plummeting deeper into depression, Debussy was unable to write at all—nine months passed without a single piece of music. His personal motto, toujours plus haut—“always higher”—had resulted in such works as the Prelude to the Afternoon of a Faun, the opera Pelléas et Mélisande, and the symphonic poem La Mer, but now his Paris study became, as he would later recall, “a factory of nothingness.”

Then came an opportunity for escape. A writer Debussy had met at one of the Tuesday night soirees hosted by the poet Stéphane Mallarmé offered the composer the use of a villa in Pourville-sur-Mer, a town he had visited before, a hundred miles away on the Normandy coast. Debussy happily accepted, and on July 12, 1915, he set off with Emma and their nine-year-old daughter for a three-month sojourn by the sea. He was 53 years old at the time, with not much longer to live.

The environs suited Debussy perfectly. He loved the villa’s tangled, rain-soaked garden, which provided a view of the English Channel, the soothing zinc-hued water making him almost forget the distant horrors of war. Soon he was dreaming of purchasing the villa—if only he had the money. It wasn’t just the tranquil setting that won him over. He felt a sense of gratitude to this place where he had discovered himself again. “I am relearning about music,” Debussy wrote from Pourville, hardly an overstatement considering the inactivity of the previous year. He was an ardent Parisian—hating to leave the capital for any reason, missing it intensely when he was away—but now the thought of going home, he wrote, sent “shivers up [his] spine.”

Debussy was a slow worker. He could spend hours getting a single chord or phrase just right. But in those three months by the sea, probably the most productive of his life, he composed, in his words, “like a madman.” He completed the suite for two pianos called En blanc et noir, as well as the first of what he hoped would be a series of six instrumental sonatas, this one for cello and piano. But it was the remarkable Douze Etudes, begun on July 23 and completed on September 29, that would go down as one of Debussy’s greatest achievements, and one of the seminal works of the 20th century.

Etudes and scales, scales and etudes—just the thought of them can conjure up memories of routine drudgery in anyone who has played an instrument. But the etude is a necessary building block in the education of every young classical musician, an exercise focused on developing a particular instrumental technique. (In French, the word étude means “study.”) Still, even pieces meant mainly for instruction can rise to the status of great art—as J. S. Bach and Domenico Scarlatti proved in the early 18th century. Not until Frédéric Chopin and Franz Liszt began composing a century later, however, did the etude really come into its own, both as a piece that could test and develop a pianist’s abilities, working the muscles and stretching the hands, and as a Romantic vehicle, filled with poetry, pathos, playfulness, and virtuosity. To play Chopin’s Etudes, opus 10 and opus 25, requires not just dexterity and skill but sensitivity, intelligence, and above all, a beating heart. The same is true of Liszt’s Paganini Etudes and 12 Transcendental Etudes, which also contain many poetic passages while pushing the bounds of what is physically possible on the keyboard. These works were meant not for the stuffy confines of the practice studio, but for the grand perch of the concert stage.

Debussy extended the possibilities of the concert etude, reinventing the genre for a new century. He had written successfully for the piano before—his two books of Preludes, composed with “the betterment of the pianistic race in France” in mind, contain some of his most beautiful and evocative music. But the 12 etudes present different kinds of challenges: the continuous passages in thirds in the set’s second piece; the joyous, tumultuous, brash octaves in the fifth; the frenetic, acrobatic passagework in the sixth; the bumblebee-like seventh, its buzzing lines demanding both accuracy and a delicate touch; the rapid, repeated 16th-note triplet patterns in the ninth; and the driving onslaught of chords in the 12th. When his publisher, Jacques Durand, admitted to having trouble with many of these obstacles, Debussy responded, “I may say there are certain passages which sometimes bring [my fingers] to a halt too. Then I have to get my breath back as though I’d been climbing a flight of stairs … In truth, this music wheels above the peaks of performance! It’ll be fertile ground for establishing records.” Debussy acknowledged that it took “the most implacable patience” just to copy out some of the etudes. Simply looking at the score—the dizzying blur of black notes surrounded by accent marks and clusters of sharps and flats—can be tiring.

Here and there are the influences of Stravinsky (the propulsive, rhythmic 12th could not have been written by a composer unfamiliar with the ballet Petrushka) and of Chopin (not surprising, given that Debussy had been working on a new edition of the Polish master’s piano works). Yet these pieces are all unmistakably, inimitably Debussy. It’s all here, the languid atmosphere, the vaguely Eastern temperament, the feeling of transience. Anyone familiar with Debussy’s music will instantly recognize the shimmering sounds of the second etude, or the hazy sensuousness of the eighth, with its feeling of free improvisation. The third etude, composed almost entirely in fourths, recalls some of Debussy’s earlier Preludes (especially La cathédrale engloutie, which depicts a sunken cathedral rising out of a tidal flood) as well as La Mer, the composer’s great ode to the sea. In another etude, the eighth, lovely undulating lines seem to evoke the rising and receding tide, and in one place in the score, Debussy has even written, “supple and wavy.” It’s not hard to imagine him taking inspiration for these pieces from the high vantage of his back garden, as he gazed upon the watery expanse, absorbing its many moods.

The pianist and writer Charles Rosen has argued that Debussy’s etudes are “as much exercises in composition as in keyboard technique; in many of them one may say that the composer has posed a problem for himself and, in solving it, has presented the pianist with another.” Consider the fourth etude, its harmonic structure cleverly based on only one interval: the sixth. Just as inventive is the second etude, where the highly chromatic passages suggest where Debussy might have gone had he lived longer, coming to atonality in his own idiosyncratic way. He knew he was breaking ground, both harmonically and in terms of sonority: “unheard-of things” is one phrase he used to describe the sound world of his etudes.

Debussy was a complicated personality, to say the least—a spoiled misfit who acted on his many impulses, insufferably grumpy, yet charming when he wanted to be. All his life, he made and lost friends with seemingly equal ease. And though he did not treat the women in his life very well, he was mad about his daughter, Chouchou. (Her given name was Claude-Emma.) He found her endlessly enchanting and took as much delight in her toys and games as she did. Playfulness was the most endearing characteristic of this grand enfant, and it should not come as a surprise that Debussy’s music is shot through with many moments that make us smile. The etudes are no exception.

“I’m sure you’ll agree with me,” Debussy wrote to Durand, “that there’s no need to make technical exercises over-somber just to appear more serious; a little charm never spoiled anything.” There’s humor from the very beginning. The first etude starts with a simple C major scale, four notes up, four notes down, calling to mind some mundane childhood exercise, but as these scales continue, they are punctuated by a series of rude, percussive A flats, and this battle between order and petulance continues amusingly as the music speeds up—to the point of nearly coming undone—until the piece turns into a rollicking affair, with the pianist’s hands flying up and down the keyboard. It’s almost as if Debussy is saying, Look at what I can do with eight simple notes and the wink of an eye.

Music was changing in a profound way in the early part of the 20th century. When compared with Stravinsky—not to mention Arnold Schoenberg, Anton Webern, and Alban Berg—Debussy was more old guard than new. Yet his 12 etudes point prophetically to the future, anticipating György Ligeti, whose own piano etudes, composed between 1985 and 2001, would imbue the genre with even greater imaginative possibilities.

Debussy left Pourville with his spirits revived, though his underlying concerns about his health must have remained. Before the end of 1915, his cancer would be diagnosed, and three years later, with German bombs falling not far from his bedroom window in Paris, he would die. How lucky, then, that he was able to get away during that summer a century ago, when all had seemed so bleak, to produce this late masterpiece. And if pianists haven’t quite embraced the etudes the way they have his earlier work, the supreme difficulties of these later pieces must have much to do with that, even if the virtuosity is never on show for its own sake. These pieces should be played more often. Full of imagination and daring, as fresh today as they must have sounded when first heard, they communicate a wide range of feeling and mood in harmonically inventive ways, while giving the pianist a supreme workout. “Everything sacred which wishes to remain sacred shrouds itself in mystery,” Mallarmé wrote. The reward for any musician who masters Debussy’s etudes, and for any listener willing to embrace them, is a peek beneath the shroud.