'Simpson' tuning

[Bill Hibbert]

Rod:

> I thought Simpson tuning referred to the sequence of overtones and
> not their relative prominence or persistence, making it possible to
> have a very poor sounding bell that technically is Simpson.

A few thoughts:
* I (and others) like to avoid the phrase 'Simpson' tuning as it is not 
very well defined - and Simpson was a plagiarist, borrowing a lot from 
Taylors' work for his published papers. Far better to refer to true-
harmonic tuning, defined as hum, prime and nominal in octaves.
* Within a true harmonic bell, there is much room for variation: 
tierce, quint and upper partials, clappering etc.
* Relative prominence of partials is probably one of the lesser 
effects. Relative partial intensity depends much on tower acoustics and 
clappering, not the bell itself.
* Some supposed 'Simpson' bells are not true-harmonic and sound poor as 
a result. Some supposed old-style bells are close to true-harmonic. A 
mixture of old-style and true-harmonic in one peal shows neither off to 
best advantage.
* It is said that proportion of tin is quite important to tone, and 
that some post-war peals suffer in tone due to metal shortages. I have 
never seen this quantified.

> how much error in the notes produced is allowed before the bell
> is no longer [true-harmonic]?

The tuning tolerance for partials within a bell (i.e. inner tuning) is 
10 cents, though usually founders tune to better than this. Extensive 
experiments suggest that 10 cents is at the limit of human ability to 
differentiate pitch. There can be much greater variations between bells 
(i.e. outer tuning) due to use of different temperaments, stretch, etc. 

> metal loss at the clapper strike point must detune.

Of course this is true, but measurements on early Taylor true-harmonic 
bells suggests the effect is not significant over a century of ringing. 
Corrosion due to atmospheric pollution on the other hand is a problem, 
and many 17th century Hemony treble bells have been replaced in 
carillons because of this.

Bill H