Carleton,
I agree with all that your organist-friend says, though I note he uses
the older nomenclature for the notes (CCCC, CCC, CC, C, C', C", etc.).
Nowadays, those are more commonly called C1, C2, C3, C4 (middle C), C5,
etc. on organs, pianos, harpsichords, etc. (Strangely, handbells and
some other instruments use the same scheme but place C5 at middle C.)
Grout's "History of Music" may discuss this, if memory serves.
Also, the example given for a pipe with an actual length of eight feet
from lip to top must be for a principle (diapason) or other
large-diameter pipe. An acoustic half-wavelength of eight feet produces
a note of frequency 70.7 Hz at a speed of sound of 345 m/s. That would
be the output of a narrow pipe. Increasing the diameter makes the
acoustic length longer (by *very* roughly half of the diameter or a
larger fraction of the width of a "square" pipe) which would account for
the frequency of 65.4075 Hz cited below. Organ pipe builders distinguish
between physical length and acoustic length, both measured from lip
(analogous to the fipple on a recorder) to end. The length of the foot
(from toe to lip) is not a factor in pitch since that merely routes the
air to the mouth. For the sake of completeness, it must be noted that we
have neglected to mention the effects of other structural factors, such
as taper (especially near the end) and placement of beards and cheeks
(pieces of metal attached below and beside the mouths).
Your friend provided an excellent description of the structure of the
ranks. I might just add for general interest what the effect is. Suppose
the organist plays middle C on a manual with 8', 4', 2', and 1-1/3'
stops pulled. The organ sounds middle C and the two Cs above it (from
the 8', 4', and 2' ranks, respectively) and the G above the the highest
C (from the 1-2/3 rank). This is related to the Pythagorean ratios.
I doubt that the names of pipe ranks will ever change and I personally
hope that they do not. I would not be surprised to see pipe builders do
their layout work in millimeters, though! I have never seen chest
pressures given in anything but "inches [of water column]", but that
could easily be changed to pascals without losing any traditional values
carried by names since measured chest pressures did not evolve until
mechanical air blowers were devised. Organ specifications given in music
catalogs will cite the ranks by name and length, but only the builders'
specs provide chest pressures.
The technically-minded are encouraged to read "The Physics of Musical
Instruments" by Fletcher and Rossing. I believe the book on organs by
Audsley (mentioned by your friend) may be considered a classical
reference on organs and is highly recommended for a somewhat less
mathematical approach. I don't have a copy of the latter on hand to
check my memory, though.
Jim
[EMAIL PROTECTED] wrote:
....
> I asked a friend of mine who is an organist about Jim's comments on organs
> yesterday ... here is his reply.
....
--
Metric Methods(SM) "Don't be late to metricate!"
James R. Frysinger, CAMS http://www.metricmethods.com/
10 Captiva Row e-mail: [EMAIL PROTECTED]
Charleston, SC 29407 phone/FAX: 843.225.6789
