Considering Craig Brougher's and other's comments on organ pipes,
I have the following comments:

There is a vast difference between organ pipes even of the same tone
name.  The variety is caused by several things:

  1) variations of pressure -- even slight changes in pressure
  2) voicers
  3) manufacturer
  4) scaling (width to length ratio, halving ratios)

The main difference between the sound of metal and that of wood
is only slightly because of the substance of which it is made.

The pipe designer sets the scaling as to diameter of metal pipe, or
width and depth of wood pipes as these measurements relate to speaking
length of pipe.  He also sets the halving ratio or the number of pipes
at which the speaking length is half the length of another.  An 8 foot
rank is called that because the low CC pipe is about 8 feet long (give
or take several inches).

One might think that an 8 foot rank would halve at the octave or at
pipe 13.  This almost never happens.  Often the pipe that is half the
length of CC is actually number 18, but that changes as well with what
voice the pipe has and what the scaler has in mind.

Different manufacturers each had their own method of scaling, making,
and voicing each pipe.  This is why certain companies were known for
certain ranks at which they excelled.  Kimball strings, for example are
greatly coveted for their beauty.  You could have 6 different company's
version of any single pipe name and have 6 different sounds.  They
would all sound similar, but obviously different.  They may all be made
from the same materials, too, but still sound different.  There are many
different ranks that have the bass pipes made of wood and trebles of
metal.  If voiced correctly even the ears of Brougher could not find
the change.

Voicing is the main thing that makes pipe tone.  I would have to say
that as many as 80% of all the pipes to be heard in organs today are
deficient in voicing.  There are many reasons for this.

1) There are very few extremely competent voicers today.  The really
good ones do _nothing_ else but voice.  They go from organ to organ
at great price and spend 8 hours or more on each 61 note rank of pipes.
Most pipe organ "builders" purchase pipes from any of several pipe
shops and do relatively little voicing.

I put the word builders in quotes because most of today's pipe organ
"builders" are merely organ compilers.  They purchase pipes, chests,
reservoirs, relay and combination systems and put the organ together.
I consider that to be a true organ builder one must build most of the
organ in the shop, including chests, pipes and consoles.  There are few
of these and they include Wicks, Reuter, Schantz, and others.  Schantz
is one of the organ builders that I know does complete voicing.

The quickest way to save money in organ building is to use the voicer
sparingly.  Wicks is known to be the most economical pipe organ built
today.  Wicks cuts no corners -- they make an organ that is designed to
function trouble free for 50 years or more.  However, they do not do
complete voicing.  They do make available to the customer the option of
hiring one of several voicers who will come to the completed organ on
a separate contract and just do voicing.  One of these voicers is in
particular demand because he is able to make a Wicks sound exactly like
an Aeolian Skinner.

2) Pressure changes can totally change the sound of even the most
perfectly voiced pipe.  One would never expect the same sounds from
high pressure (8"-20") theater organ pipework as found in low pressure
(2"-4") classical pipework.  When a pipe is voiced it is imperative
that it be played at the EXACT pressure that it was voiced on.  This
is why final voicing of an organ is always done in the finished organ.

It is not final voicing unless it is done on the exact chest that will
play it and at the exact pressure.  You take the perfectly voiced pipe
and change the pressure even 1/2" in water lift pressure and you will
hear a different sound.  Too often what we hear are older pipes that
are compiled from several sources and put into the same organ and
expected to sound right.

A good voicer can make it work, but they are scarce and very expensive.
Usually the pipes each had a different pressure they were originally
voiced on, but now they are playing all on the same pressure.  On too
high of a pressure pipes will sound forced or overblow to the octave or
12th.  On too low a pressure they will sound dull.  And in either case
the pipes will not speak correctly.  The ictus or beginning of the
speech will be too slow or too fast.

A few good people are able to revoice pipes to drastically change the
pressure at which they play.  The higher pressure pipework requires
a higher cutup or height of mouth hole while lower pressure pipework
needs a lower cutup.  Very high pressure pipes will have arched mouths.
The actual cutup is the top of the arch, but the sides of the arch are
what grips the speech and keeps it from overblowing at those high
pressures.

I hope I have cleared up some questions folks may have had.  I hope
I have not further muddied the waters.

D. L. Bullock    Piano World    St. Louis
Dallas Pipe Organ Service.