The main goal of this thesis was to develop tools and methods for creating new music for the Japanese bamboo flute shakuhachi. Shakuhachi is an end-blown bamboo flute, which has existed in Japan since the seventh century. The oldest shakuhachi solo repertoire, honkyoku, can be considered as “tone-color melodies”, where the expression is primarily happening through microtonal alterations of pitch and timbre, while the melody is secondary. An early fascination with timbre led the author to the shakuhachi and its sound aesthetics, and towards exploring new methods for making music. The main method described is composing through improvisation, using nonlinearity to focus on the present with the sound and timbre of shakuhachi. To learn about unconscious factors during music making, a micro-phenomenological interview method is used, aiming to reach a deeper understanding of the decision-making and the pre-reflective experience during improvisation. The history, learning methods, aesthetics, and concepts of Japanese traditional shakuhachi music are explored to give inspiration and context for the work, in the search for a personal musical expression within the tradition. Analysis of timbral gestures is conducted to further research the timbral aspect of Japanese traditional music, as well as to analyze the musical connection between Japanese traditional shakuhachi music and the music composed in the project.