This article describes the process and techniques involved in the tuning of a pipe organ.
Generally speaking, the temperament of a pipe organ is part of its design, and is not lightly changed during its lifetime.
The pitch of an organ cannot be significantly changed without major work, as pipes need to be shortened or lengthened.
Another important preparation step is to stabilize the temperature of the building in which the organ resides.
If one holds a small metal flue pipe briefly in one's hand and then returns it to the chest (windchest), its pitch (relative to a tuning reference) can be heard to change as the pipe returns to room temperature.
The audibility of these harmonics is extremely sensitive to the position of one's ears relative to the pipes.
These devices must be carefully monitored and managed to avoid creating the opposite problem.
In fact, controlling the climate around a pipe organ can have a significant impact on its tuning and maintenance schedule.