I have always marveled at the mastery of Renaissance composers. Responsorium (12'03") (2009) is my first attempt, modeled after Missa pro defunctis (1605) by late Renaissance Spanish composer Tomas Luis de Victoria (1548-1611), to build a rule system that makes possible the integration of a plainchant melody into twelve-tone harmonies. The piece consists of "Cantus" and contrasting "Versus" sections. While harmonies are rather static in the Cantus sections, pitch-class sets are constantly transformed in the Versus sections according to the pitches of the D-Dorian melody. All the voice leading and the transformations are strictly regulated by the rule system implemented in my own Java program. The program generated score files for the sound synthesis and processing software "RTcmix," developed by Brad Garton. And its channel vocoder, phase vocoder, and various filter instruments, written by John Gibson, process the vocal sounds and produce all the synthesized sounds in real time.