This chapter is an overview of the characteristic sound properties of flue organ pipes. The characteristic properties of the stationary spectrum and attack transient have been surveyed and assigned to properties of the physical systems (air column as acoustic resonator, air jet as hydrodynamic oscillator, and pipe wall as mechanical resonator) involved in the sound generation process. The measurements presented underline the primary role of the acoustic resonator in the stationary sound and of the edge tone in the attack.
