It is a premise of Unification Thought that art possesses unifying aspects. These aspects have both internal (content) and external characteristics (form).
Aaron Copland's life's work can be said to be a synthesis of musical styles. His early works were influence by jazz and displayed an affinity to fuse divergent styles into a highly expressive compositional syntax. His Clarinet Concerto (written for the jazz legend Benny Goodman) displays a facile ability to live in two musical worlds—jazz and classical.
Copland, like Charles Ives before him, would base much of his music on American folklore and in this respect he can be considered a "nationalist" composer in much the same way Modeste Mussorgsky or Nikolai Rimsky-Korsakov are Russian nationalist composers. Like other "nationalist" composers, his music reflects the Principles of Unity of Content and Form as expressed in Unification Thought's Theory of Art. By utilizing folk idioms (content) and synthesizing them with "classical" conventions (form), Copland's most popular music achieves a sublime balance reflective of Unification Thought's unifying ideals.
Rather than merely quoting folk music, the melodic, rhythmic and harmonic properties of his music are infused with the musical characteristics of folk tradition. His vibrant score, El Salon Mexico, incorporates Mexican rhythmic, harmonic and melodic elements with traditional European orchestration and is highly evocative of the Mexican spirit, especially in the syncopated rhythmic aspects which are typical of Latin dance music. This is a realization of Unification Thought’s unifying principle in art.
The term populist implies a sensitivity towards the virtues of common people. At a time when modern composition had become increasing complex and progressive, Copland's populist simplicity was the polar opposite of the avant-garde of the early twentieth century. Socially, the arcane, acerbic and highly formulaic music of the Second Viennese School (Arnold Schoenberg, Alban Berg, Anton Webern), was viewed as being increasingly elitist—and to a certain extent, anti-social—whereas Copland's folk influenced scores, rooted in tonal and pan-tonal conventions, evoked a spirit of community and social inclusion. The country dances, the hymn-like melodies, the sweeping, pan-diatonic harmonies that comprise his most popular works, have made his music the subject of great admiration and appreciation.
Unification Thought’s Theory of Art asserts that: "Art is the unity of various correlative activities and elements in creating beauty."
One of these correlative activities is described as Unity of Creation and Appreciation, where appreciation is as important in the artistic process as the creative aspect. When the principles of unification are utilized in any creative endeavor it can be said that art is fulfilling its original purpose. A part of that purpose is to assist in achieving greater conditions of unity and harmony into the everyday experience. Copland's populist utterances can be said to embody the principle of Unity of Creation and Appreciation in that they allow for an appreciation of his music that is highly inclusive.