Tubas and Pipe Organs


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Posted by AW on February 22, 2003 at 15:18:25:

In the "8va heroes" thread below, some mention was made of low-pitched organ pipes. In other threads, people have mentioned pipe organ like sound. Since I regularly deal with both pipe organs and with tubas, I would like to comment on the similarities and differences. In both cases these wind instrumtents form the bottom of an ensemble. I would say that it is extremely rare for an organist to use only the lowest pipes in a solo manner, while it is merely not very common for a tuba to play a solo as a member of a larger ensemble.

For the benefit of those who are familiar with tubas but not with the details of pipe organs, I would like to furnish a few facts:

First of all, real 64-foot pitch organ stops that go all the way down to the bottom C (to 8Hz) are found in only two instruments in the world, in Atlantic Ciey, USA and Sydney, Australia. Other large organs only have 32-stops (to 16Hz) for the lowest, and the majority of organs bottom out with 16-foot stops (to 32Hz).

A large pipe organ might have as many as four 32-foot stops, typically three sets of flue pipes and one set of reed pipes: flute (perhaps labeled Contra Bourdon 32) with a lot of fundamental and very little harmonic development, diapason (perhaps labeled Contra Principal 32) with both fundamental and good harmonic development, "string" (very narrow scale) (perhaps labeled Contra Violone 32) with little fundamental and plenty of harmonics, and finally a loud reed (perhaps labeled Contra Bombarde 32) with plenty of building-shaking fundamental and plenty of harmonics, both in tune and out of tune.

What is striking about the three flue (basically making their sound like a whistle) stops
is the contrast between how well they can give wonderful support to a chorus of other organ stops on one hand, and on the other hand how unimpressive it is when these pipes are sounded by themselves. It's hard to believe it unless you hear it in person.

The kind of stop labeled Contra Bombarde 32 (or Tuba Profunda 32) is impressive in any situation. Played by itself it is sometimes described by organ builders as "the sound of a dinosaur coughing up a jackhammer." In some installations, this kind of stop (as well as the somewhat related Contra Diaphone 32) has had to have its wind pressure reduced, in order to avoid structural damage to the building. I know of cases where a lockout mechanism had to be installed to prevent the organist from playing two of these pipes in the same octave, as the resulting beat tones would cause building damage. This has got to be the stuff of young macho tubist fantasies! Anyway, it does a great job of supporting the FULL ensemble. However, a good organist would never use it alone, even though that sound is impressive (but not in a positive way!).

Why don't tubas have much fundamental in their low notes? Any organ builder can answer that question. A resonator (the body of a organ pipe, the entire length or a tuba) must be acoustically opaque for the frequencies you want it to be a resonator for. An organ pipe made of thin and light material will have little fundamental. In order to get a nice solid, fundamental 32-foot CCCC (16Hz), one will need (beside a few horsepower of blower) is a resonator that is not transparent at 16Hz. Thus one large-scale 32-foot diapason pipe can, by itself, weigh over 2000 pounds, and be made of an alloy that is over three quarters lead. A wooden pipe at the same pitch would have walls a few inches thick. A 32-foot pipe that is to be mostly harmonics will be thinner and will be of an alloy that is mostly tin. Tubas are made from thin brass that does well confining the higher harmonics, but is pretty transparent to the low fundamentals. OK tubists, you want to make a stone floor shake? Now you know what is needed. Please post photos of you playing your multi-thousand pound instrument!

To me, as a tuba is played lower and lower below its "cash register" gets thin and rattling, and has uses that become more and more rare and specialized. Using one of these low and fundamentalless notes can give a great support to an ensemble in which the other octaves are already represented. But, without all of that coverage, the sound of a tuba in its pedal range can make a non-tubist say things that range from, "why bother,?" to "how awful." It's just like some of those organ pipes that were never built or voiced to be used by themselves. A good organist knows when they should be used in support of a chorus of other sounds and pitches.

Allen Walker



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