This project presents the results of the analysis of the compositional techniques used by Claude Debussy in his Sonata for Violin and Piano and Sonata for Cello and Piano. These two pieces share five compositional techniques in common: use of four-note pitch collections, slight changes in intervallic relationships, repetition of small patterns, use of special techniques, and small leaps. Also explored are the ways in which Debussy’s compositional style in these two pieces differ from his earlier style. Given that both works were written within the last five years of his life, they are representative of his mature style. Debussy was notable for developing and popularizing the 20th century French style known as Impressionism, though he did not refer to his music by this term. His music avoided traditions set forth in the Classical and Romantic eras, doing so by using new compositional tools. Debussy’s early works often used pentatonic, hexatonic, and octatonic pitch collections to create a skewed sense of harmonic direction. Both sonatas seek to achieve this same goal but do so through the above five techniques. Though Debussy still occasionally uses these collections, he is less reliant on them to achieve his signature sound.