Acoustics Bulletin Jul-Aug 2011 - Institute of Acoustics

INSTITUTE
AFFAIRS
Meeting report: South-west branch
Mike Wright. Lance Foy, organ builder - an intuitive acoustician
Could this have been the first ever meeting of the South West branch
of the Institute of Acoustics in Cornwall After months of planning
(and some debate over the number of people who would make the long
drive to Truro on a Saturday morning) seven IOA members attended on 7
May 2011. They were accompanied by members’ friends and partners, plus
a few local organists, who enjoyed a most informative and entertaining day.
Lance Foy is well known in the West Country as one of the finest organ
builders around. Rumours abound in Dorset, Devon and Cornwall that if
Lance Foy had not worked on a particular instrument, it was not worth
working on! That may be something of an overstatement but his name
appears on the brass plates of organs in Camborne, Falmouth, Plymouth,
Great Torrington and Barnstaple to name but a few. From a listing of the
National Pipe Organ Register there is evidence that he has been
responsible for the sound of at least 150 different organs he has built,
restored and modified. The visit featured some of the finest instruments of
the south-west right in the centre of Truro.
The morning session was held at Truro Methodist Church in Union Place.
Lance Foy firstly gave a brief history of the organ from its humble origins,
starting with the ‘hydraulis’ in Greece in the 3rd Century. On these
instruments, the wind supply was created by water pressure. Bellows were
later introduced as a means to provide wind for the pipes and by the 17th
Century, the classical organ as we know it now had been developed.
However, he also pointed out the fact that there are now very few
surviving early English organs made before the Reformation of the 16th
Century as most were destroyed at that time.
Lance Foy went on to explain how a pipe organ works by describing flue
pipe as working in the same manner as a recorder or a whistle. Air under
pressure (referred to as wind) is driven down a flue and against a sharp lip
called a labium, causing the column of air in the pipe to resonate at a
frequency determined by the pipe length. A reed pipe is one that is
sounded by a vibrating brass strip - a reed - where the wind is directed
towards the reed, which then vibrates at a specific pitch. Nowadays, the air
is supplied at various pressures to ensure that as few or as many of these
pipes as the player wishes can function properly at the same time.
He then moved on to the mechanics that take the actions of the organist
using the keyboards (‘manuals’) and pedals to the place where the sound
is produced at each pipe. He described the pros and cons of the various
methods of achieving this objective. These range from basic mechanical
systems of connecting levers and rods (known as a ‘tracker action’)
through to the later pneumatic systems that were needed to cater for the
larger instruments that became common in the 19th Century. He then
moved on to describe the more modern electrical systems. However, he
was keen to explain that whilst less direct systems may make for a rather
less strenuous effort on behalf of the organist, there can be significant time
delays after pressing a key or pedal before anything starts to
happen! Such delays are in addition to the ‘speaking time’ of a pipe
which tends to be greatest at lower frequencies. The organ at Truro
Methodist Church was originally built in 1895 and had a pneumatic action.
This was later replaced in the 1950s with electrical relays that were not
particularly satisfactory. Lance Foy completely rebuilt the organ in 1983
with new actions and much enhancement of the tonal scheme.
The organist and choirmaster of Truro Methodist Church, Phil Davey,
assisted Lance Foy by illustrating the various ‘ranks’ of pipes which are
controlled by the ‘stops’, as he selected them singularly and in combination,
to demonstrate the wide range of sounds that were possible.
Lance then explained about the pitch produced by an organ pipe, which is
a function of its length. The wavelength of the sound produced by an open
pipe is approximately twice its length. If the longest pipe, pitched at C, is 8
feet (2.4m) in length, the pipe one octave higher will be 4 feet long, and two
octaves above (middle C) will be 2 feet long. A closed (stopped) pipe
produces a sound one octave lower than an open pipe.
The nomenclature of a ‘rank’ of open pipes (diapason) was explained
further. This refers to the length of the longest pipe in the rank. Thus the
longest pipe (C2) two octaves
below middle C (C4) is 8 feet
(2.4m) long. In a rank of stopped
pipes, the lowest pipe is 4 feet
(1.2m) in length but sounds at
unison pitch, so it is known as an
‘8ft stop’. Assuming the organ is
tuned to ‘standard concert pitch’,
A = 440Hz and tuned in equal
temperament, then 'middle C'
(C4) has a frequency of
261.626Hz. Lance Foy explained
the work he undertook in a
further rebuild of 2009 to change
the organ to ‘standard concert
pitch’. Before this restoration
work, A was approximately
449Hz, making it impossible to
play the instrument in
Range of organ pipes
Lance Foy explains a
mechanical system!
combination with any other fixed pitch instruments. To achieve the lower
pitch meant that the lowest 16 foot pipes in the ‘Double Diapason’ rank
were not large enough to be corrected. As a result, Lance Foy was obliged
to use modern ‘digital technology’ to complete this rank of pipes and at
the same time, introduce a new 32 foot (C0 or just over 16Hz) ‘Sub
Bourdon’ stop to enrich the depth of sound. The pitch range is illustrated
in the Figure.
Phil Davey demonstrates the fine organ at Truro Methodist Church
12 Acoustics Bulletin July/August 2011