How to Play the Pipe organ
Points to remember when playing the pipe organ

Without having visited the location of a specific organ and tried playing, it is impossible to know what sound it will make. The true charm of the pipe organ is that every one is custom made.
You could have a stop list to choose from, like a restaurant menu, and an idea of what kind of timbres it might be possible to produce beforehand, all in a tentative sense, but there are of course various things that need to be tried out at the actual location, such as which timbres can be combined to produce the timbre sound you had in mind.
There are a great variety of things one might wish to know before a performance, such as the timbres that have been combined by different organists through the years to play each piece, the intention of the composer, and other factors. It is for this reason that the preparation requires time and effort.

In hot summer periods, when the temperature doesn't drop for an extended period, pipe organs become hot and can go out of tune. If only the exterior is cooled such problems will still occur, so it is important to cool the instrument throughout. Differences in room temperature at the top and the bottom of the pipes may produce undesirable results, and in some cases air-conditioning is used for up to 24 hours to ensure that temperature is consistent across the whole instrument.