Stravinsky's use of Russian folk melodies is most evident in his early works, such as his ballet "The Firebird" (1910) and his opera "Petrushka" (1911). In these works, Stravinsky incorporates traditional Russian melodies and rhythms into his compositions, creating a distinctly Russian sound.
However, Stravinsky's use of Russian folk music was not limited to his early works. He continued to incorporate elements of Russian folk music into his compositions throughout his career, even after he had left Russia and settled in the United States. For example, his Symphony of Psalms (1930) contains a movement based on a Russian folk song, and his Concerto for Piano and Wind Instruments (1923) incorporates Russian folk melodies into its final movement.
Stravinsky's use of Russian folk music was not simply a matter of nostalgia. He was drawn to the beauty and vitality of Russian folk music, and he believed that it could provide a rich source of inspiration for his own compositions. By incorporating Russian folk music into his works, Stravinsky helped to bring Russian culture to a wider audience and to promote a greater understanding of Russian music.