tuben will be able to comment on this...

[jamsav]

and I thought my ear was getting better...similar experience all season- 3 different venues , played in all previous, and wicked flat this year !! Who tunes these ? and to what ??? I dont remember if there are any other variables that I am 100% certain of,- the churches are either hot or cold - but I"ve been pulling slides for the past 3 weeks !! js

[scottw]

I played a midnight last night, doing a brass/organ piece, and, sure enough, I was pulling from the first run-through, even in a [to me] rather chilly sanctuary. Weird.

[iiipopes]

It's not just the ambient temperature. It's the proximity to an exterior wall, so that the organ is actually colder than the ambient temperature would seem. It's the temperature of the pipes, not just the air, that is causing the flatness. As we all know, conduction is a more efficient way to change temperature than convection or radiation, and if the pipe chests are mounted to a wall, then the heat is going right out of them, causing them to go flat.

Another aspect is the placement of the blower. The blower is usually some considerable distance away from the chests in most pipe organs, in order to isolate the noise. If this also in the basement or near an exterior wall, then the pipes are going to be fed with cold air instead of the relatively warmer ambient air in the worship space, to the same effect.

Tuben can give better examples and some more technical aspects of just how far out of tune, but I believe these are the main two causes.

[scottw]

When dealing with pipe organs (as a fixed pitch instrument), the pitch changes by 2 cents for every degree of temperature change. Colder = Flatter / Warmer = Sharper.

Piano pitch: Warmer = Flatter / Colder = Sharper (warm strings expand)

Organ pitch:

Tuben,
These 2 statements seem to directly contradict each other. Would you please educate me why these are both correct in this instance? This is interesting.

[iiipopes]

It's not just the ambient temperature. It's the proximity to an exterior wall, so that the organ is actually colder than the ambient temperature would seem. It's the temperature of the pipes, not just the air, that is causing the flatness. As we all know, conduction is a more efficient way to change temperature than convection or radiation, and if the pipe chests are mounted to a wall, then the heat is going right out of them, causing them to go flat.

The temperature of the pipes is a factor, but no more than the ambient air temperature. While conduction is more efficient, the wind chests are ALWAYS made of wood (99% hardwood), and wood is a good insulator.

Another aspect is the placement of the blower. The blower is usually some considerable distance away from the chests in most pipe organs, in order to isolate the noise. If this also in the basement or near an exterior wall, then the pipes are going to be fed with cold air instead of the relatively warmer ambient air in the worship space, to the same effect.

True, but in MOST organs, the builder was aware of this and the blower is located in a space that is at least climate controlled and usually supplied with air from the space the organ lives in. In some rare examples, extensive HVAC ducting is directly ran from the organ space to the blower to supply the same air.

RC

I stand corrected.

[pgym]

The fact that pianos go flat with warmer temperatures is due to a mechanical rather than physical reaction. With warmer temperatures, the steel and copper strings of a piano expand, loosen (slightly), and they go flat.

Slight quibble: thermal expansion of materials is a thermodynamic property of materials, so it's a physical reaction.

[tbn.al]

Robert just played a gig with me at my church and fortunately did not have to pull the Wizard all the way out, but only by divine providence. I was having a general discussion with the choir director a week before the performance to coordinate the preparations when she mentioned that the organ had just been tuned( not by Robert). My ears perked up when she said the tuner had purposely tuned the organ to 438 because, " the abient resonance of the room dictated that the organ should be tuned to 438 for its best sound." She also mentioned that she felt compelled to have the piano tuned down to match. I calmly suggested that she might want to check with the concertmaster, a hired gun from the symphony, before the first rehearsal. The violinist was of course mortified at the thought of tuning the orchestra down and responed to the effect that if she wanted any semblance of pitch or any resonance from the strings she should revisit the tuning issue with the organ tuner. The organ was begrudgingly retuned and the piano to match. The concert was wonderful and Robert was a delight to blend with as always, even if I did throw him a couple of ringer parts. If I can figure out how to do it, I'll post a recording of him playing the fool out of an electric bass line on a rock tune with the HS choir. The Wizard is rockin' and a rollin'.

[scottw]

When dealing with pipe organs (as a fixed pitch instrument), the pitch changes by 2 cents for every degree of temperature change. Colder = Flatter / Warmer = Sharper.

Piano pitch: Warmer = Flatter / Colder = Sharper (warm strings expand)

Organ pitch:

Tuben,
These 2 statements seem to directly contradict each other. Would you please educate me why these are both correct in this instance? This is interesting.

Pitch increases with temperature increase in organ pipes because the column of air inside the pipe vibrates faster while the length of the pipe remains unchanged.

The fact that pianos go flat with warmer temperatures is due to a mechanical rather than physical reaction. With warmer temperatures, the steel and copper strings of a piano expand, loosen (slightly), and they go flat.

RC

Not trying to be obtuse here, but wouldn't the girth and length of the pipes themselves increase or decrease with a change in temperature, much as would the piano string? Would this not produce a change opposite from that which you describe, ie, that the air column would change in size with the expansion and contraction? This is my thing learnt for the day!

[scottw]

Interesting. Thanks for adding to my knowledge of things I thought I knew.
What would cause a higher wind pressure? Or a lower? As these would change pitch, what would protect against change?
Does temperature cause the wind pressure to increase or decrease? Or, is it a mechanical thing?

[tubashaman2]

.

[tubajazzo]

from my own experience as church organ player (more in my former years) i can say that organs in winter are terrible, at least in our climate here in Germany. The church is more or less cold the whole week, but for the service it is heated. The organ often sits on an upper gallery, elevated from the ground. There it is even warmer. The outer pipes get the warmth, but the inner pipes (the majority) stay cold. The worst are the stops called trumpet, trombone etc (Zungenstimmen, don't know the english term). Therefore organs are mostly finetuned in spring or summer. Changeing the whole pitch of an organ is a major event....

Gerd

[pgym]

I

No, the pipes are not prone to differences in length due to temperature changes. (Definitely not diameter change)
As I said, the length of the pipe does not change with temperature

Sorry, but unless organ-builders are building pipes from a material that violates the known laws of physics, the pipes DO change in length and diameter due to temperature: just not enough to be a significant factor.

The coefficient of thermal expansion for brass pipes, for example, is 1.9x10^-5m/degree C, so given a 10m long, 25cm diameter brass pipe, raising the temperature from 65°F to 75°F (5.556°C) would change the length by 1.055mm and the diameter by 0.0026mm.

[tubajazzo]

does your tuba change its length with temperature? not really, ok not significantly. Does the pitch change? yes. Same with organ pipes of the flute type.

[rocksanddirt]

Interesting thread.

slightly off topic comment, but related to tuning management.....

In our church, the HVAC is kept on to keep the temp above about 65 during the winter and below about 80 during the summer in order to avoid having to tune the organ, and piano every week in order to use them. Generally our organ (a fairly small "parlor" one) and piano are tuned to match and stay at about A=440 without much drama.

Another church our kids school uses for assemblies sometimes, avoids this by having all music be electronically generated (keyboard, drum machine, electric guitars, all vocals mic'd), even though the place is small enough to not need any amplification whatsoever.

[pgym]

I

No, the pipes are not prone to differences in length due to temperature changes. (Definitely not diameter change)
As I said, the length of the pipe does not change with temperature

Sorry, but unless organ-builders are building pipes from a material that violates the known laws of physics, the pipes DO change in length and diameter due to temperature: just not enough to be a significant factor.

The coefficient of thermal expansion for brass pipes, for example, is 1.9x10^-5m/degree C, so given a 10m long, 25cm diameter brass pipe, raising the temperature from 65°F to 75°F (5.556°C) would change the length by 1.055mm and the diameter by 0.0026mm.

Fine, BY LAW they change but not enough to matter. What is the coefficient of thermal expansion for a pipe made of 50% tin & 50% lead? 75% tin 25% lead? 95% lead 5% impurities? Our pipes are not made of brass (with a few exceptions).

http://www.engineeringtoolbox.com/linea ... -d_95.html" target="_blank

What is the expansion of sugar pine? Or mahogany? (Most large pipes are made of wood, and some small ones too)

http://scholarsarchive.library.oregonst ... 487ocr.pdf" target="_blank



(And, of course, for unsealed wood pipes, the length, diameter, and thickness of the pipe wall will also be affected by the humidity.)

Also, we would never tune the organ at 65F knowing the normal occupied temp were closer to 70F.

Doesn't matter what temp you tune at: a change in temp from whatever temp the organ was tuned to will produce a change of length, ΔL = αΔTLo where α = the coefficient of thermal expansion of the material the pipe is made of, ΔT is the difference between the tuning and the target temperature, and Lo is the length of the pipe at the temperature the organ was tuned at.

[shovelingtom]

That's actually a .001% change in length. 10 meters expands ~1 millimeter. It's insignificant.

[iiipopes]

Indeed it is insignificant. On a standard moderate diameter CC open diapason pipe, moderately blown in the classical manner, of a "nominal" 8-foot speaking length, it takes about an inch of movement of the tuning slide up or down to make the same change in pitch that a few degrees of temperature difference makes, not a millimeter.

[sloan]

Doesn't matter what temp you tune at: a change in temp from whatever temp the organ was tuned to will produce a change of length, ΔL = αΔTLo where α = the coefficient of thermal expansion of the material the pipe is made of, ΔT is the difference between the tuning and the target temperature, and Lo is the length of the pipe at the temperature the organ was tuned at.

Please do the arithmetic. CALCULATE how much the pipe changes in length when the temperature goes up by X degrees. And then, CALCULATE how much the speed of sound changes for the same change in temperature.

Now you are ready to CALCULATE the change in pitch due to the change in length, and the change in pitch due to the change in the speed of sound.

And then, you will know the truth, and the truth will be in you.

[king2ba]

I'm just happy when I play the right notes....what's this intonation thing y'all are talking about?

[Ken Herrick]

I'm just happy when I play the right notes....what's this intonation thing y'all are talking about?

i think it might have something to do with Gregory Chanting away in the background - or is it what Boodist monkies do in the jungle.

Anyway, it ain't so much the note bing right or wrong - it's the feeling that counts.