At the time they were cast, the carillons and bells of the van Aerschodts were highly praised. They claimed to tune their bells, and there is evidence they had a tuning machine. Séverin in his prospectuses said that he could cast bells with either a minor or a major third (ref 2 page 167), and there is evidence of this in the foundry books. On the other hand, André Lehr says ‘the van Aerschodt carillons are undoubtedly made up of very handsomely cast bells, but the overtones of these bells sound utterly confused’ (ref 1 page 209). The foundry book records show that the strike notes of bells were being tuned, but there is no evidence for the tuning of any other partials.
I have compared the hum and prime intervals for 118 van Aerschodt bells with those of 887 bells cast by Rudhall, and Mears prior to their adoption of true-harmonic tuning. None of the bells included have been tuned since they were cast. Here are plots of the hum and prime intervals:
What is clear from these two plots is that the hums in van Aerschodt bells are centred much closer to the true-harmonic ideal of -2400 cents, and the primes much closer to -1200 cents. The spread of values is also a little less. Here are the figures:
| van Aerschodt | Rudhall / Mears | |||
|---|---|---|---|---|
| Partial | Average | Standard dev. | Average | Standard dev. |
| Hum | -2371.1 | 52.1 | -2266.5 | 68.7 |
| Prime | -1224.4 | 60.4 | -1295.9 | 89.9 |
It is interesting to look at how the hum and prime tuning in the two different groups of bells changes with the size of the bell, i.e. the change with nominal frequency:
In the van Aerschodt bells, apart from very small bells, the primes are consistent across all sizes of bells from the very large to the very small. The hums show a very slight flattening in smaller bells. For the Mears and Rudhall bells, the primes get very significantly flatter in the smaller bells up to nominals of around 1750 Hz (which is a weight of roughly 200kg or 4cwt). Mears and Rudhall smaller bells were cast to ringing weights, i.e. thick and heavy, to give them handling characteristics more suited to a ringing peal. Due to lack of knowledge of bell design, this gave them flat primes. In contrast, small van Aerschodt bells were cast to lighter chiming weights, allowing them to maintain the prime tuning. The trebles of van Aerschodt bells hung for full-circle ringing were generally too light.
As regards tuning of nominals or strike notes to the musical scale, the investigations at Two van Aerschodt carillons, Simpson, van Aerschodt and Lower Beeding, and Strike Notes and tuning of old-style bells show that the strike notes of van Aerschodt, Rudhall and Mears bells were tuned by ear. The founders were tuning to the musical scale using strike notes estimated by ear against a tuning standard, rather than direct measurement of nominal frequencies. The strike notes of the carillons at Eaton Hall and Philadelphia and the ringing peals before tuning at Lower Beeding, Kilburn and Lye were investigated, a total of 76 bells. The standard deviation of the strike notes against equal temperament in the van Aerschodt bells is 22 cents. For the historic UK founders, the standard deviation of strike notes against the temperament they used is 11 cents. So the historic UK founders were able to tune strike notes twice as accurately as the van Aerschodts. The discrepancy in strike note tuning of the van Aerschodt bells is significantly worse in the smallest bells, especially at Eaton Hall, and some bells are almost a semitone sharp.
The van Aerschodts claimed to be able to cast bells with minor and major tierces at will (ref 2 page 167). Of the 68 bells for which I have seen the foundry book entries, 47 have a description of the tierce tuning, typically ‘tierze majeur’, ‘majeur’, ‘tierze mineur’ or ‘mineur’. However, there is no correlation between this description and the actual tierce tuning, which on average is a just minor third in all bells. What caused the founders to believe they were casting major third bells is not clear.
In summary, the moderately accurate hums and primes in all but the smallest van Aerschodt bells mean that individual bells sound sweet, or sonerous. As bells for change ringing, van Aerschodt bells do not sound too bad, though their trebles are too light. However, in a chime or carillon, the poor tuning of the strike notes or nominals, and the inexact octaves, mean that the musical effect is poor, as can be heard in this recording of the Eaton Hall carillon.
References
- André Lehr, The Art of the Carillon in the Low Countries, Lannoo 1991.
- Luc Rombouts, Singing Bronze, Lipsius Leuven 2014.