John Norman

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Matching Organs to Acoustics

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

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"

15 Baxendale, London N20 0EG |

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