How did Claude Debussy’s music help change 20th-century classical music?

Claude Debussy was a seminal force in 20th-century music, fundamentally altering the landscape of classical composition by challenging 19th-century traditions. His influence manifested through several key innovations:12

• Harmonic Innovation: Debussy moved away from functional tonality, often employing whole-tone scales and treating dissonant chords—such as seventh chords—as self-sufficient harmonies rather than elements requiring resolution. This approach disrupted traditional harmonic progression and paved the way for new musical languages.34
• Orchestral Color: He revolutionized instrumentation by treating individual instruments as soloists and focusing on the evocative, coloristic potential of woodwinds, brass, and strings, rather than adhering to rigid, lyrical, or functional roles.5
• Structural Freedom: By avoiding traditional musical form, Debussy created works that prioritized atmosphere and "shimmering" textures, aligning his music with the ideals of Impressionist and Symbolist artists.14

His methods cast a long shadow over the century, influencing diverse composers such as Igor Stravinsky, Béla Bartók, and Maurice Ravel, and ultimately helping to dismantle the academic constraints of the previous era.435