There have been two works titled "Rainbow Machine" in the past: one is "Monody for Two Players," commissioned in 2008 for performance by the unit "ROSCO" (Fumiko Kai (violin) + Kaori Osuga (piano)), and the other is "No. 2: Seven Irradiations," written in response to a request from Tsubasa Tanaka, whom I met in a class I taught at the former Yotsuya Art Studium. This "Koan-001" is the third work, created with a concept similar to both previous works and utilizing a further developed algorithm. This was not intended to series the works under this title, but rather because I felt something was still "lacking" in both of the previous two works as compositions. In other words, under the premise that Hiroaki Ooi, who also commissioned this work, would perform it, I attempted to fully "realize" the 2008 idea of "Rainbow Machine" through this work. Similar to the previous two works, the monody automatically generated by a self-feedback system based on the stacking of perfect fifths constantly changes its musical "mood" by varying its range, clarity of tonality, and other elements during the process. However, it goes without saying that the origin of this "mood" lies on our human side, as we can only react delicately and "like a machine" to the continuously changing melodic patterns. (Masahiro Miwa)