This excerpt from the six-movement Missa Charles Darwin depicts one of Darwin's finches through the solmization of nucleobases found in a portion of its DNA. The melody derived by assigning the letters A, G, T, and C to pitches serves as the launching point for a musical setting of one of Darwin's texts on natural selection placed alongside the opening of the Latin mass (Lord have mercy, Christ have mercy). The juxtaposition of the two themes — one the supplication for mercy, the other the foundation for something that is not inherently merciful — provides the underlying drama for the selection.