”Collective improvisation,” a collaborative method from the 1960-1970's western avant-garde theaters, was implanted to Taiwan in the 1980's by those who had studied abroad, and then utilized by numerous theaters in experimental new productions. The ”Performance Workshop Theatre,” directed by Stan Lai, which applied these methods in productions, is now a leading theater company, with Lai the method's most representative figure in Taiwan. Soon after returning from abroad, Lai adopted a relatively open, permissive, improvisational method. In three productions from his first creative period, The Days We Were, Reaching for the Stars, and Bach Variations, he avoided pre-conceptualized structure or theatrical form, and sprang simply from a single concept or theme, allowing all participants to contribute to build up the performance text. Afterwards, with the abundant performing segments generated from collaboration and improvisation, the director gradually either cut, collaged or combined them with brilliant results in the completed piece. This production method is not Lai's own creation, however, as it can be traced back to ”The Open Theater” led by Joseph Chaikin and his direct follower, Shireen Strooker, with whom Lai collaborated, from ”Amsterdam Werkteater.” Bach Variations (1985), has long been regarded the most experimental and artistic production among all of Lai's early works. The core research issue lies in these points: First, how Lai utilizes the composition concept of Bach's Fugue as a starting point to create a non-narrative, extremely musical style of performance text for this play. Secondly, how the director searched for this concept's ideal performing style, to objectify the theme: full of impermanence, life resembles variations of Bach's Fugue, but is unlike Bach's mathematical, rational and neat music. These serious challenges for the director of creations like Bach Variations, inspired by this kind of abstract and obscure method of improvisation, stand as the main focus of this paper.