Aaron Copland’s final compositions include two chamber works for flute, the Duo for Flute and Piano (1971) and Threnodies I and II (1971 and 1973), all written as memorial tributes. This study will examine the Duo and Threnodies as examples of the composer’s late style with special attention given to Copland’s tendency to adopt and reinterpret material from outside sources and his desire to be liberated from his own popular style of the 1940s. The Duo, written in memory of flutist William Kincaid, is a representative example of Copland’s 1940s popular style. The piece incorporates jazz, boogie-woogie, ragtime, hymnody, Hebraic chant, medieval music, Russian primitivism, war-like passages, pastoral depictions, folk elements, and Indian exoticisms. The piece also contains a direct borrowing from Copland’s film scores The North Star (1943) and Something Wild (1961). Several expressive elements in this Vietnam-era piece relate to war and peace, shedding light on Copland’s views of the artist’s role in a war-torn society. Threnody I was composed as a tribute to Igor Stravinsky. Unlike the Duo, the piece outwardly appears independent from Copland’s 1940s idiom in its canonic, neoclassical treatment. However, the work quotes a Spanish song from Kurt Schindler’s Folk Music and Poetry of Spain and Portugal. This finding suggests that even while employing modernist techniques in the Threnody I, Copland was still incorporating 1940s ideas with specific folk connections. In 1973 Copland composed Threnody II, a memorial tribute in honor of Beatrice Cunningham, a personal friend. The distinctly modernist work employs tone rows in the forms of motives and harmonic dyads. The tone row is nevertheless combined with Copland’s signature wide intervals and relaxed pastoral style. By drawing upon score analysis; published texts by Copland, his contemporaries, and outside scholars; related literary and cultural sources; and Copland’s unpublished letters, manuscripts, and related documents in the Copland Collection at the Library of Congress, this thesis provides insight into the end of the composer’s career by highlighting his interest in borrowed sources even as he sought to create music that was new.