French composer, whose harmonic innovations helped pave the way for the musical upheavals of the 20th century.
Debussy was born in Saint-Germain-en-Laye on Aug. 22, 1862, and educated at the Paris Conservatoire, which he entered at the age of 10. He traveled to Florence, Venice, Vienna, and Moscow in 1879 as private musician to Nadejda von Meck (1831–94), patron of Russian composer Peter Ilich Tchaikovsky. While in Russia Debussy became acquainted with the music of such Russian composers as Tchaikovsky, Aleksandr Borodin, Mily Balakirev, and Modest Mussorgsky and with Russian folk and gypsy music. He won the much coveted Grand Prix de Rome in 1884 for his cantata L’enfant prodigue (The Prodigal Son). He then studied in Rome for two years, according to the terms of the award, and submitted new compositions regularly but unsuccessfully to the Grand Prix committee. Among these were the symphonic suite Printemps and a cantata, La demoiselle élue, based on a poem, "The Blessed Damosel," by the British writer Dante Gabriel Rossetti.

Early Works
During the 1890s Debussy's works were performed with increasing frequency, and despite their then-controversial nature, he began to gain some recognition as a composer. Outstanding are the String Quartet in G Minor (1893), which some critics regard as his best work; and the famed Prélude à l'après-midi d'un faune (Prelude to the Afternoon of a Faun, 1894), his first mature orchestral work. The latter was based on a poem by the French symbolist Stéphane Mallarmé.
Debussy's opera Pelléas et Mélisande, based on the play of the same name by the Belgian poet Maurice Maeterlinck, was produced in 1902. It earned Debussy widespread fame as a musician of outstanding significance. The extent to which his score retained and enhanced the abstract, dreamlike quality of Maeterlinck's play was extraordinary, as was his treatment of melody; in his hands, the latter became virtually an extension, or duplication, of the rhythm of natural speech. Regarded by some critics as a perfectly wedded fusion of music and drama, it has had frequent revivals.
From 1902 to 1910 Debussy wrote chiefly for the piano. Among the most important works of this period were Estampes (Engravings, 1903), L'île joyeuse (The Isle of Mirth, 1904), Images (two series, 1905 and 1907), and many preludes. He rejected the traditionally percussive approach to the piano, instead emphasizing the instrument's capabilities for delicate expressiveness.
In 1909 Debussy learned that he was afflicted with cancer, from which he died on March 25, 1918. Most of the works he produced during his last years were for chamber ensembles.

Forerunner of Modern Style
The music of Debussy's fully mature style was the forerunner of much modern music and made him one of the most important late 19th- and early 20th-century composers. His innovations were chiefly harmonic. Although he did not devise the whole-tone scale, he was the first composer to exploit it successfully. His treatment of chords was radical in its time; he arranged chord progressions in such a way as to weaken, rather than support, the illusion of any specified key. The lack of fixed tonality produced a vague, dreamy character that some contemporary critics termed musical impressionism, after the resemblance they saw between it and the pictorial effect achieved by painters of the impressionist school; the term is still used in describing his music. Debussy himself did not create a new school of composition, but he liberated music from the limitations of traditional harmony; moreover, the high quality of his own works proved to subsequent composers the validity of experimenting with new ideas and techniques.
Among Debussy's numerous other important works are the ballet score Jeux (Frolics, 1912), the orchestral poem La mer (The Sea, 1905), and the songs Cinq poèmes de Baudelaire (Five poems of Baudelaire, 1889).