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Extracts from a paper read at the
Royal Academy of Music
to a seminar organised by the
Institute of Acoustics
Visual issues are too often given priority over acoustics and music
A good position for an organ becomes more important if the acoustic is less reverberant
Never allow non-reflective surfaces such as carpets to be put in front of an organ
The player has to hear both instrument and other musicians in context
This wonderful photograph shows how pointless it is to be able to play the organ from out of earshot !
Playing a west-end organ from an east end console is nearly always a disaster
Moderate detachment may be acceptable in a reverberant building
Architects (starting with Christopher Wren) usually make organ cases too "woody"
Organbuilder-designed cases are more transparent to sound than they appear
This slide shows a view looking out from inside a case by "Father" Bernard Smith
The Victorians often put organs in organ chambers. Organbuilders then omitted upper casework
This example shows an organ buried in a former Lady Chapel.
Case roofs increase the precision of attack
- good for Bach
- perhaps less good for Elgar
Number of Stops
The more stops there are the more fun the organ is to play
But we need to relate the number of stops to the acoustic power needed
Example
Church 120 ft long, 50 ft wide and average 30 ft high
Reverberation with congregation present
1.5 seconds
6,000 sq ft units of absorption
= Six stops on the Great organ
More absorption
needs a bigger organ
An organ tucked away in a chamber needs to be bigger
But too big an instrument, real or imitation, always sounds false when reduced to an acceptable power
Atmospheric Absorption of the Treble
This is the phenomenon that most people ignore
Takes the edge off the treble in a "live" acoustic
But leaves an exposed edginess in a "dead" acoustic
This has consequences !
Norman & Beard noticed the effect 100 years ago
Used different pipe scales for the choruses of organs in buildings with a dead acoustic
Wider and flutier trebles to compensate for the "edgier" acoustic
The Cut up is the voicer's secret weapon
Organ builders who used low cut ups - e.g. Samuel Green and G.M.Holdich - made sucessful organs for unreverberant venues
Father Willis used higher cut-ups; his best organs were all for venues with lively acoustics
Organbuilders used to Continental Abbeys sometimes fail to adapt when faced with relatively 'dead' UK buildings
Atmospheric Absorption of the Treble
also affects the choice of the best tuning
The absorption is significant in a "live" acoustic so the acid of Equal Temperament helps to avoid an over-bland "tutti"
In a dead acoustic, without this absorption, Equal temperament can be unpleasant
The graph shows just how large the errors are in the most-used keys with ET tuning
Nevertheless ET is right in a "live" acoustic where the acoustic itself will take off the rough edges
Thomas Young (or its near relative Valotti) is best in more intimate and unreverberant environments
Neidhardt is a compromise tuning that has now found considerable acceptance where the acoustics are "in between"