[Sergei Rachmaninoff, "Vespers (All-Night Vigil)" ]
Musical nationalism: The use in art music of materials that are identifiably national or regional in character. These may include actual indigenous music or melodies, rhythms or other features that are conventionally regarded as recalling indigenous music.
Melodic Variation: A technique of modifying a melody, usually after its first appearance in a composition.
Harmonic Variation: A technique of modifying the harmonic
structure after its first appearance in a composition while other
musical elements such a s melody remain constant.