This article is not about human organs (but if you think your organs need tuning, Quezi's pseudoscience department has a link for you). No, it's about pipe organs. Of course, pipe organs must be tuned when they are installed, but do they need retuning? The pipes just sit there in a big, substantial housing, so how can they get out of tune?
Electronic organs don't need re-tuning, indeed cannot be re-tuned, although better ones can have their tuning adjusted by just turning a knob to be played with historical instruments that are lower pitched than modern ones.
Pipe organs, however, do need re-tuning. Organists keep a logbook of tuning and other problems with their organ. The king of instruments is sensitive to humidity and temperature, and since the pipes are made of both metal and wood they react differently, and also the pipes are differently exposed to changes in humidity and temperature depending on their placement in the housing and in the building itself, since some large organs have remotely placed registers.
Tuning an organ is much more complicated than tuning any other instrument, since the different registers have to be tuned to match each other. The most common tuning tool is called a “tuning knife”. It is a piece of metal used to tap gently on the tuning mechanism of a pipe, so as to avoid touching the pipe with the hands.
An organ builder once said that there are seventeen different ways to change the pitch of an organ pipe. Wikipedia's article on the subject mentions eleven, and describes them as follows:
“The techniques for tuning flue pipes vary with the construction of the pipe:
- A stopped pipe is usually tuned by moving its stopper up or down
- A capped pipe is usually tuned by moving its cap up or down
- On a slotted metal pipe, some or all of the metal cut out to make the slot is rolled up so that the
slot can effectively b
e shortened or lengthened, thus changing the pitch of the pipe
- On a slotted wooden pipe, a wooden slider is provided to shorten or lengthen the slot
- A conical metal pipe will sometimes have a tuning slide, but may be tuned by moving the large ears on either side of the pipe's mouth
- An open metal pipe usually has a sliding collar at the top of the pipe that can be moved to change the pitch
- Small metal pipes are often “cone tuned”, whereby the top of each pipe is deformed inward or outward using a heavy hollow cone. Such tuning is extremely stable, but at the cost of gradual damage to the pipe over time.
- An open wooden pipe usually has a metal flap partially covering its top, which can be rolled or unrolled, or bent upward or downward.
Reed pipes may be tuned in any of several ways:
- by lengthening or shortening the vibrating length of the reed tongue by means of a wire protruding from the boot of the pipe,
- by adjusting the effective speaking length of the resonator, or
- by adjusting the metal flap in the side of the resonator or the cap on the top of the pipe (especially with fractional length pipes)
All of these methods can also affect the tonal regulation of the pipe, so tuning reed pipes is trickier than tuning flue pipes.”
Flue pipes produce the sound in the same way as a recorder or whistle. The pipes may look the same length, or they may be graduated in length to look good on the front of the organ. If their top is exposed, they have either a stopper or a slot on the back of the pipe that determines the pitch.
There are several informative websites on the subject, such as this one:
YouTube also has several videos that demonstrate the tuning of the different types of organ pipes and let one hear what the tuner is doing.
According to Praetorius, the reed stops of pipe organs required constant tuning; he emphasized the fact that the pitch of the stop fell in summer and rose in winter. The pitch of the other stops rose in summer and fell in winter.
Praetorius (1571-1921) was a German organist and composer. In his time, the temperature changes in churches were more extreme than now.
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