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 počmes de Baudelaire (Five poems of Baudelaire, 1889).