Temperature and Humidity

Recommendations for Pipe Organs

We are often asked why the pipe organ is not at A440 when we leave after a tuning call. Or we are asked to tune the pipe organ to the piano.
The response to these questions is not as straight forward or as simple as it seems.

Some facts about pitch

The American music industry reached an informal standard of A=440 Hz in 1926. Some began using it in instrument manufacturing at that time. The American Standards Association recommended that the A above middle C (A4) be tuned to 440 Hz in 1936. This standard was taken up by the International Organization for Standardization (ISO) in 1955 as a recommendation and was it was then formalized in 1975. So, it is possible your pipe organ was not originally designed to be tuned at the A440 pitch (now considered Standard Concert Pitch) if it was manufactured before 1975.

The only way to find out accurately what the pitch of your pipe organ will be when you use it is to have the temperature in the room surrounding the instrument set to exactly what it will be on Sunday when the room is filled to capacity. In other words, conditions in the room must be as close as possible to what they will be when you will be using the organ. Only then can you really measure accurately what the pitch of your pipe organ is. However, even if it is 70 degrees Fahrenheit in the room where you measure the pitch, that is not a guarantee that it will be 70 degrees within the organ chambers and throughout all the components and divisions of the organ. It takes much longer for the components in the organ to stabilize in temperature than it does for the surrounding air. You might feel comfortable and warm but the temperature of the wood and metal in the pipe organ is still changing and not necessarily at the same rate.

In the wildly variable Canadian climate, it can often be much colder in the organ chambers during the winter months and much warmer during the summer months which accounts for the fact that the organ pitch varies so much from season to season and sometimes even from day to day. Especially if the organ chambers have been placed on an outside wall with the hot sun shining on the walls. The sun can heat the inside of that organ chamber up like the inside of an automobile. That is why we recommend that your pipe organ be tuned every year when the seasons change, typically in the spring and fall.

Pipe organs are like every other wind instrument. Their pitch varies with the temperature. When the air is cool, pipes will sound flat. When the air is warm, pipes will sound sharp. This is because the air inside the pipe is less dense when it is warm and therefore oscillates faster. Pipe organs will change in pitch approximately 2 cents per degree Fahrenheit of temperature change. Pianos, on the other hand, become sharp as the temperature drops and flatten as the temperature rises, although not at the same rate as a wind instrument.

What you should and shouldn't expect from a general organ tuning

The pitch of your pipe organ is not adjusted or changed during an organ tuning. The pitch was established by the organ voicer during the tonal finishing of your pipe organ, when the instrument was manufactured and installed in your church. The voicer determines things like the timbre/tone, pitch, volume, and attack of each specific pipe by manipulating the design, shape, and length of the pipe. The acoustics in the room are a big part of the final result as is the temperature in the room. The pipe organ builder will voice the organ when the temperature in the room is stable, most often at 70 degrees Fahrenheit, but the final results are limited by the pipes they are working with and the design of the room.

Not all pipes are affected by temperature at the same rate. Reed pipes such as Trumpets and Oboes rise and fall at a slower rate than flue pipes. This is why it is so important that the temperature in the room is turned up well in advance so it is stable at that temperature when the organ is tuned. It is also important that the room be brought to within two degrees of that temperature when the organ is used in functions, to ensure proper tuning. Playing the organ at lower or higher temperatures will not damage the organ, but the tuning, especially between the reeds and the flues, will be sour.

As mentioned above, the pitch of the pipe organ can also be affected by the number of people in the room. A room at full capacity will heat up so an organ that might start out at A440 can end up sharp by the end of a performance as the bodies present warm the room. In some extreme cases, even leaving the expression shutters closed for a prolonged period of time during a performance can affect the pitch of the division behind those shutters.

The organ chambers should be heated passively from the room, and there should be no vents or fans blowing directly towards the pipework.


Although the organ will not be in tune if the temperature is turned down when the building is not being used, there are some advantages to lowering the thermostat. A lower temperature setting means the furnace will not be cycling on as often so the humidity in the room will stay higher. The tuning and pitch will return to normal when the temperature is turned up and stable again.

Of equal concern is the effect of humidity on an organ relative to the temperature. Most of the large parts of an organ (chests especially) are made with wood, which swells and compresses as the humidity changes. These wood parts are especially affected over time by dry conditions, brought about by artificial heating. Leather is also affected by humidity. These effects are often exacerbated by the fact that organs are often installed higher in the building, where the temperature is even higher, and the relative humidity swings are more exaggerated. If the air in the room is not humidified in the winter, it is probably best to allow the room temperature to fall back, to reduce the usual plunge of the relative humidity of the air. Air circulation systems can also help mix the very hot air at the top of a tall building and mix it with the cooler air below. Air conditioning is less of an issue as far as humidity is concerned. Carefully placed humidifiers may provide marginal help, however, the most ideal scenario for overcoming winter dryness is a humidification system that humidifies the air in the whole room. This will not only help the organ but will also extend the life of any other musical instruments, such as a piano, or any wood furniture present.

General recommendations

In an ideal world the temperature surrounding the organ would be maintained at 70 degrees Fahrenheit (21 degrees Celsius) and never exceed 105 degrees Fahrenheit (40 degrees Celsius) or go below 45 degrees Fahrenheit (10 degrees Celsius). Humidity of the organ room should be kept between 50 percent and 60 percent. The maximum should never exceed 80 percent and the minimum level should never fall below 30 percent.

Sudden or extreme temperature changes must be avoided, otherwise permanent damage might be caused to the organ. Raising and lowering of the temperature should be done gradually at a maximum rate of plus or minus 2 degrees Fahrenheit per hour (plus or minus 1.5 degrees Celsius per hour). The basic reason for increasing and lowering the temperature of the ambient air very slowly is to make sure that the dew point will never be reached. Excess of humidity and excessive dryness can be dangerous to a pipe organ.

Rapid cooling of a room may raise the relative humidity to the dew point and cause condensation that would be harmful to the leather, the metal parts, and the very sensitive mechanism of the instrument. Rapid heating of a room may dry the chests and other large wooden parts too quickly around the edges and cause splitting.

No part of the organ should be subject to direct radiation of heat (strong lights or sun). Concentration of warm or cold air around the organ must be avoided. Temperature should be uniform throughout the room. Consequently, lighting, air duct intakes or outlets (heating or air-conditioning) should not be installed near an organ nor should they blow air toward it, for not only could it put the organ out of tune, but air ducts could create a concentration of polluted air that can cause rapid deterioration of some materials. An HVAC system may increase the air movement in the organ room and around it, causing instability in the speech and tuning of the pipes. It is important to note that air movement in and around the organ should not exceed 2' per second with or without such systems.

Final thoughts

Our goal during a pipe organ tuning is to ensure the organ is in tune within itself. We ask for the temperature to be stabilized in the room before tunings (we recommend ten to twelve hours at Sunday’s setting) so that the pitch is what it will be when the organ is used. If, after reading all of this, you still insist on having the organ in tune with the piano, it is the piano that should be repitched and tuned to the organ. Not the other way around. It is relatively easy to repitch a piano. Repitching the hundreds if not thousands of pipes in a pipe organ is a much more time consuming and therefore expensive operation which often involves cutting pipes permanently. Not something that is done during the scope of a general tuning, or when the temperature outside is extremely hot or cold. When the piano tuner comes to tune, the temperature in the room should be set and stable, as it would be for an organ tuning, so that the organ pitch is what it will be when the organ is used. The piano tuner can take their reference from the pipe organ using A below middle C on the Great Principal 4’ stop. (A very stable flue stop.)

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revised November 29, 2023
by Barbara Dodington