Pien, meaning transformation, is synonymous with the i of I Ching. In philosophy, i evolves from simplicity to complexity, complexity to phenomena, phenomena to its conglomeration and dispersion, and finally invariability.
Also at work is the yin-yang concept of complement, which controls instrumental interaction. The piano and winds, the pitched entity, alternate horizontally to form a composite line, while the percussion, the nonpitched entity, interacts vertically with the pitched entity by amplifying and reflecting its material.
Pien uses six variable modes. Their progression “takes the form of six interacting textures, each of which has not only six variable modes in pitch organization but also six each in the organizations of duration, intensity, and articulation.” These thematic, rhythmic and timbral cells, constantly recombined, produce prismatic gatherings and dispersals of energy.