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Organ Air Conditioning


Chris Woollard

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I very recently visited friends living in central Germany who happen to have a very nice house organ of 11 stops resident in their largest room.

Certainly a splendid instrument. Very high quality pipe work. Playing it is a delight.

Germans tend to be very green indeed so I was a little surprised to see a rather large air conditioning unit installed in that room only.

This is simply there for the organ. Before this they had only a very nice Steinway B with no special provision other than a humidifier for extreme winter weather. The organ apparently demanded the air conditioner, but not for continual use. They seem to play mostly on weekends and so during hot weather week days the organ gets hot. On weekends the A/C brings the temperature of that room down to a nominal 22 degrees.

 

Is this a sensible way to stop organs from turning into a giant celeste during extreme weather. I must admit I have a similar problem at home. Has anyone observed similar provisions, for organs small or large. Is this a standard provision for concert organs.

 

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Hi

 

Organs need a constant temperature to stay in tune. The pitch of reeds shifts less with temperature fluctuations then flue pipes - and I suspect some flues shift at slightly different amounts too. The only solution - especially if you need the organ to be at a standard pitch for use with other instruments is to maintain that temperature - establish it a few hours before the organ is needed. I've read that some cinema organs had thermostatically controlled electric heaters in the chambers - but obviously, that doesn;t work with unenclosed pipework. Air flow through swell boxes is another issue - which is why the normal prctice is to leave swells open when the organ isn't being used (except with totally enclosed organs).

 

Do away with reeds and, as long as the organ is only played by itself, then a well constructed instrument will hold tune for long periods - go for cone tuned metal pipework and that becomes several decades - the pitch will shift with temperature, but within normal domestic limits, everything shifts at the same rate, so it sounds in tune.

 

You can't buck the laws of physics!

 

Every Blessing

 

Tony

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It is true that the laws of physics are difficult to buck, though for organ pipes the uninitiated can sometimes be taken by surprise. Prepare for a sermon.

 

As temperature rises the pipes get longer because the metal expands, therefore it is a common misconception that organs go flat in hot weather. In fact they go sharp, because the speed of sound increases, and the frequency (pitch) of a flue pipe is directly proportional to sound speed. Simple arithmetic shows that the pitch variations due to sound speed are far more pronounced than those due to the metal expanding.

 

For a flue pipe, pitch changes by approximately 3 cents per degree Celsius (a cent is one hundredth of a semitone), therefore a 10 degree temperature change results in pipes going out of tune by about a third of a semitone. This is a significant amount of course, and it is only because the pitch of all the flue pipes changes in about the same ratio that an organ can continue to be used at all. However the reeds are a law unto themselves and predicting their behaviour is more difficult, which is why they often cannot be used with the fluework until the tuner next arrives. Unfortunately s/he then often just tunes the reeds (not the flues), and often just at the wire, and over time this can throw them badly out of regulation and off-speech. This is because a reed needs to be tuned both at the wire and at the resonator so the tube continues to resonate at the correct frequency. But this a time-consuming and more expensive procedure. And the longer the tuning process takes, the more likely it is that the wind temperature goes up anyway owing to the blower getting hot or the ambient temperature rising. And so it goes on ....

 

The pronounced sensitivity of pitch to temperature also explains the need for other instruments playing with an organ to retune several times during a concert of extended duration, particularly as a large audience can cause a hall to warm up.

 

Several practical implications follow. One is that frequent and thorough tunings are necessary to keep a pipe organ in tip-top playing condition. Once a month is not unusual for those in the more prestigious venues. Another is that the electronic sound generation gubbins of hybrid pipe-digital instruments must track these pronounced variations of pipe pitch with temperature. This is especially critical because the pipes in such instruments are often flues rather than reeds (reed sounds are often delegated to the electronics), and it is the fluework which is most strongly affected. Manufacturers of such instruments usually claim that they have solved this problem, so it is valid for one to enquire how effective the temperature compensation process actually is, perhaps by asking for a live demonstration, before committing to a purchase.

 

CEP

 

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Thanks for that explanation Colin - interesting arithmetic observation that although metal (though presumably not wood) pipes slightly lengthen in hot weather, the effect of the speed of sound in hotter air more than cancels out the effect of the longer pipes so that pitch actually sharpens.

 

But I'm puzzled by your suggestion that pipes increase in pitch by three cents per degree Centigrade - that implies that between a freezing winter and a hot summer, which could see a change of 30 degrees centigrade, the metal flue pipes will be potentially a semitone sharper in the summer. I can't say I've ever noticed such a dramatic change, and indeed if pitch was affected to that extent they would be unplayable not only with reeds but also with wood flues. Furthermore, I thought the adage was that reed tuning was affected more by temperature fluctuations than flues - are you suggesting that reeds actually stay better in tune than flues, and that when the organ sounds out of tune in summer, it's the reeds that are in tune and everything else is out of tune? Why do we find reeds unplayable with metal flues when wood flues remain in tune with metal flues in summer?

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A lot of questions here, so it depends on how detailed you want the answers to be! Trying to be brief:

 

 

that implies that between a freezing winter and a hot summer, which could see a change of 30 degrees centigrade, the metal flue pipes will be potentially a semitone sharper in the summer.

 

Yes, the numbers above do imply that on the face of it. However the temperature coefficient of sound speed varies with absolute temperature, so the sum you did isn't quite that simple. And the compensating effect of the thermal expansion of the pipes will be a factor over such a large temperature change. But there will still be a pretty dramatic change of pitch with a 30 degree temperature change. A saving grace is that, although the outside air temperatures can easily vary by 30 degrees, those in most buildings will not because they are heated. Even if they are not, the massive thermal capacity of a large stone edifice such as a church means that it will be somewhat warmer inside than the outside air in winter, and cooler in summer - this is highly noticeable because many people make a beeline for a church if they see one on a hot day when they are out for a walk.

 

 

I can't say I've ever noticed such a dramatic change

 

Maybe that's because a tuner would have descended once or twice between the depths of winter and the height of summer, and he might have tweaked the fluework as well as the reeds if it was that badly out of tune. The tuners I have worked with have done that, though they didn't if they thought they could get in and out quickly, and onto the next job. (This is not being rude to tuners, but they are hard-pressed, and if it ain't broke, don't fix it ... Such a mindset is attractive to the customer too, because shorter tuner's visits cost less.)

 

 

if pitch was affected to that extent they would be unplayable ... with reeds

 

Correct.

 

 

but also with wood flues

 

No, because sound speed in both metal and wood pipes is affected in the same way and therefore their tuning will drift together - not by identical amounts, because over such a large temperature change (30 degrees) the differences in the thermal expansion coefficients of wood and metal, though small, will start to become noticeable.

 

 

I thought the adage was that reed tuning was affected more by temperature fluctuations than flues

 

No, it's the other way round. Reeds are usually more stable with temperature.

 

 

- are you suggesting that reeds actually stay better in tune than flues, and that when the organ sounds out of tune in summer, it's the reeds that are in tune

 

A qualified "yes" to both questions. However it's not that that the reeds don't drift at all, it's that they drift less than the flues. But because there are fewer reed stops than flues, it's quicker for a tuner to adjust them rather than the flues.

 

 

Why do we find reeds unplayable with metal flues when wood flues remain in tune with metal flues in summer?

 

Metal and wood flues drift similarly (apart from minor differences associated with differences in thermal expansion), so they remain tolerably in tune. The reeds drift differently to both metal and wood flues, so they become unplayable with both types if not tuned from time to time.

 

As there are several if not many professional organ builders on this forum, besides its owner, perhaps their perspectives might be of interest? (Well, not "perhaps" at all - "definitely" is a better word!)

 

CEP

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Hi

 

I have a recording somewhere of a service using organ & piano & a few other instruments. it was recorded in the summer of 1977 in a packed church (around 700) with totally inadequate ventilation. The pitch of the pipe organ shifts upwards something like 1/2 a semitone during the evening.

 

I'e also noticed drastic pitch shifts on the organ formerly in Rye Baptist church - in the depths of winter with no heating it would drop to somewhere around concert pitch - by the time the building had heated up (and especially come the carol service during an evening when heating had been running all day for morning service & then rehearsals it would have gone upat least to its normal half a semi-tone or so above A=440Hz - sometimes even higher.

 

Every Blessing

 

Tony

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This discussion raises many interesting points. The HIP (did British people ever use that acronym?) questions of authentic pitch for eg the music of Bach (Kammerton & Chorton) are meaningless unless we factor in the time of day and year and the resultant likely temperature.

 

And while orchestral string instruments would be going flat with rising temperatures at the same time as the organ's pitch was rising wouldn't the wind and brass instruments be rising along with the organ? And that's before we take into account the way the pitch of orchestral musicians is affected by their excitement and adrenaline levels. And how our perception of pitch is affected by timbre.

 

I'm sure I've read that in the old days organists were adept at tuning the reed stops on the organs that they used (as they would be equally adept at tuning harpsichords and clavichords in their care). For this reason reeds were the most accessible pipes. But would the organists have been competent to tune the reeds at the top of the resonator as well as at the wire?

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The tuning of organ pipes is strongly temperature-dependent - that's a fact. But it's an equally plain fact that the solution to the problem is simply to tune the instrument often enough in the majority of cases where the environment is not closely and continuously controlled in terms of temperature and humidity. The large and expensive organs in cathedrals, concert halls, etc are (on the whole) tuned often enough, so no problems there other than things like orchestras having to make minor adjustments during a concert. But this strategy - frequent tuning - costs money.

 

Local churches and other cash-strapped owners of pipe organs cannot afford frequent and thorough tuning, so they will and do suffer from the problems under discussion here. That will always have been so during the long history of the organ.

 

It certainly did exercise organ builders from the 17th century onwards when most of the written records we still possess began to be compiled. A famous example is Andreas Werckmeister who punned c. 1698 "Schnarrwerk, ist unterweilen Narrwerk" (reedwork is the work of fools). His near-contemporary, Gottfried Silbermann, also seems to have disliked reeds so much that he did not include them in the manual divisions of many of his smaller instruments, presumably because he anticipated their owners would not keep them in proper tune. He compensated by including the most wonderfully complete flue choruses going up to 1 foot pitch, thus allowing the included mutations to be used for synthetic tone building (ersatz reeds). He followed this strategy in just about all of his 'small' (actually quite large by our standards) two manual village organs such as those at Reinhardstgrimma, Fraureuth, etc. This was in a region of Germany which was subject to pretty extreme temperature variations over a year, so presumably these flue-only organs stayed tolerably in tune with themselves without needing excessively frequent tunings.

 

But because the actual pitches of these instruments would have fluctuated one from another, this is one reason why there is so much perplexing variation between the so-called pitch standards of those days. Another issue is that travel was so difficult, therefore there would not have been nearly so much travelling between churches as there is now - many people would simply not have been aware that there was a problem.

 

I appealed above for organ builders' perspectives on these matters, so while waiting for it, an excellent survey of the subject is given by Dominic Gwynn (of the firm Goetze and Gwynn) at:

 

http://www.rscm.com/assets/info_resources/Gwynn_article.pdf

 

Section 4 is particularly relevant, and it confirms the points made in the current discussion. However there is also much else of interest in this article.

 

CEP

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The Dominic Gwynn article is excellent, thank you Colin for posting the link. The little organ I tried had a new form of blower which supplied wind at an absolutely constant pressure no matter what the wind demand. I believe to save space in the design no reservoir being required. I did get to play a recent organ inspired by very old instruments which was hand blown with a deliberately unsteady wind, large wedge bellows with nothing else to steady the wind. The flue stops of this organ were indeed somewhat out of tune with each other (there was an electric blower option) but the flexible wind masked this effectively producing a rather different sound. Very interesting for early music apart from the pedal reed which was simply too loud. Looks like I will have to try some form of room temperature control also. I would not be surprised if open toe voicing accentuates the problem as very tiny changes in dimensions between lower lip and languid change the voicing.

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Regarding the regular tuning of large organs, in my experience it's a hallmark of a really good instrument that it stands well in tune. The Harrison at Belfast Cathedral rarely needed more than a few touches to a few pipes. Following on from this, I think it's also true that a lot of tuning tends to make an organ need a lot more tuning. If the pipes stand well in tune without being touched, they will do so for a long time, but if they have to be tapped around, the stability will lessen and a vicious circle will be set up.

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  • 2 weeks later...

I absolutely agree with David. My experience is that the less you mess around with tuning the better. Generally the fluework should stand well between one annual tuning and the next. The reeds will need to be moved to stay with the flues as temperature changes but it is absolutely a waste of time trying to retune with the heating on because the front of the organ will respond to building temperature changes at a different rate to that of the back and large pipes 'warm up' more slowly than small ones. What works very well for us, with a large two manual with three swell reeds, is to retune the reeds on days when the building temperature has been stable for several days. So I tune reeds at 12 C, 14 C in the winter and 16, 18 and 20 in the summer. The other golden rule is: don't be too fussy, if it's just a little bit out leave it alone and if it's nearly right then don't mess it about. And try and move the pitch when tuning as little as possible - this needs a sensitive touch as the tuning wires will often vary in stiffness from one note to the next.

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