This book deals with the physics of flue organ pipes. For centuries, the construction of organs depended on the instinct of experienced builders. Under the leadership of the Fraunhofer Institute in recent decades, scientists have developed a new and more theoretical approach to the understanding of flue organ pipes. The "Time domain study on flue organ pipes" presents and analyzes the newest advances in the effort of developing a theoretical model of a flue organ pipe. It describes the relation of the sound travelling inside the pipe's resonator with its variable terminating geometries. The analysis is based on measurements using the method of impulse reflectometry applied on varying tube terminations. Tested were tube ends of actual pipes as well as simplified terminations derived from these. The results support and reconfirm the efforts to develop a theoretical model that defines the superposition of reflections originating from open and reflected parts of the termination. Furthermore the effect of the "rough" organ pipe sound, which organ builders aim to avoid, and its corresponding phenomena in the frequency domain - the "frequency comb" - are investigated. The results of this in depth analysis allow a theoretical description of their existence.