A Quartet for Percussion
Echoes from the Gorge is the magnum opus of Chou: it represents a summation of all the concepts, East and West, acquired throughout his career. This work deploys vast timbral resources, yet is unprecedented in the thoroughness with which it codifies certain Western percussion practices according to  timbres,  sticks with regards to articulation, and contact location on the instruments. Such extensive codification results in a vast network of intrinsic structures comparable to Chinese ideograms.
[Shown at left: Chinese subtitles for each movement.] The concept of calligraphy, in which, according to Chou, “the desired contour and texture of a character are achieved by the flow of ink through a coordination of pressure, direction, speed and viscosity,” is also at work. The predetermined form in this piece emerges as the spontaneous manifestation of a continual directional change, as in the movement of a brush under the calligrapher’s control. And The Fallen Petals, the orchestral work employing this same principle, prompts historian H.H. Stuckenschmidt to call Chou a “musical calligrapher.” The yinyang concept of interaction controls the way the instruments relate to one another. The four parts, each with its own distinct rhythm derived from a single source, along with such elements as timbre and register, interact continually to create a totality in motion.
Rather than assuming a Western form, this work employs an elaborate design derived from “the preeminent musical form in East Asia, wherein all sections of a composition are elaborations or reductions of one and the same nuclear idea,” Chou explains. Echoes from the Gorge contains an introduction followed by twelve sections, each being subtitled with an evocative imagery as in ch’in music, including “echoes from the gorge,” “clear moon,” and “falling rocks and flying spray.”
As with Varèse’s Ionisation, Echoes from the Gorge explores the structural value of musical elements other than that of pitch. Perhaps it is more than a coincidence that Chou regards Ionisation as the most representative work of Varèse, wherein all the composer’s concepts are revealed. Without any conscious intention by Chou, his piece is a fitting tribute to Varèse.