Sesquialtera
by Colin Jilks

ORGANISTS and Choirmasters, if successful, will not only be blessed musically but will possess both perception and patience. Communicating musical ideas to a choir is not always easy. There was one chap I knew - an Organist of a very high C of E church at Woodford, North East London, on the borders of Essex - who was not only a brilliant organist but was able,
somehow, to command instant and continued attention from his choir.

He was a man perhaps not in the first flush of youth, and although tall, it was a tallness modified by a slightly hunched posture. His demeanour was not aided by his thick round spectacles, which magnified his eyes as he blinked knowingly through them. But standing in front of his choir he had instant authority. He was one of those unusual people who, if he only read pages from the local telephone directory, would still be received with moist spaniel eyed attention by his ladies, and his men, a
respect normally only afforded high ranking officers.

His métier, however, did not extend to the mechanics of his organ; here he was, like us, mortal. Unfortunately, his Swell organ's fifteenth stop had started to have tantrums and would not come on, or go off, but remained defiantly "half on", making his Swell resemble a Scotsman's bagpipes being warmed up.

The organ was a moderate two-manual c1900 "Bishop", which had been rebuilt by HN&B in 1969. It had a new console and electric action, as well as some mixtures and a 2ft block flute, to give that pseudo-continental sound of the time. The electrical actions and cables to the organ from the console proved to be in good order, and investigation revealed the fault to be a leaking "pan" in the Swell drawstop machine which,although electrified during the 1969 rebuild, still
contain their original leathers.

Drawstop machines come in many different varieties: some have large "ribbed" power motors, which push or pull a stop on or off, other drawstop machines have internal leather "pans" which work rather like pistons in a steam engine. These have inlet and exhaust valves to energize one side of the piston with the other exhausting to the outside air, the valves can then be reversed to energize the other side of the drawstop "pan" to take the stop off again. The pressures used are usually no more than for the organ's normal pipe wind, being about 3˝ inches, but because the drawstop pan has a large surface area its pushing power is proportionally high. An organ tuner' s fingers can be painfully squashed if an assistant inadvertently operates a stop while adjustments are being carried out.

However, our choirmaster's drawstop machine was probably some ninety or more years old. The internal sheepskin leather fitted to this machine will have had a very long natural life but must, of course, eventually fail. With a large "pan", which could be some fifteen inches long by five inches wide, the leather is thick and strong and also has added strength with wooden inserts fitted each side, which help transmit the movement. But a hole will eventually appear in the leather after many years, small at first, but gradually enlarging until the loss of pressure results in the stop failing completely, although smaller holes can go unnoticed for years.

Leather is never completely uniform in structure, rather like our skin with its spots and pimples, and a weak spot will eventually reveal itself. Disconnecting and returning the faulty drawstop machine to our workshop enabled complete dismantling and the replacement of the internal leathers.

Good as they are, drawstop machines can be bulky and take up valuable space in the organ chamber. As an alternative, many organ builders now fit electric solenoids, which are considerably smaller and still provide a finger squashing firmness in operation. These solenoids are cylindrical, some three to four inches in diameter and about nine inches long. A steel central rod connects the unit to the drawstop slide and is operated by the unit's internal electro-magnetic coils; they also have felted disc-stops at each end to control the movement's travel.

Cleverly, they also include an electronic switching device which shuts off the electric current when the required movement has been completed, preventing an excessive drain on the low voltage system. These units are designed to run on the normal 12/16 volt DC output of an organ transformer/rectifier and it's good to know they are made and supplied by a small specialist company based at Swanley, Kent.     

Although tracker actions are now de rigueur for almost all new organs these days, electric solenoids are invariably used for drawstop actions and, where assistance is needed for coupling, small solenoids or magnets become invaluable. Sometimes soundboards can have two sets of pallets, the main mechanically operated one, and a second pallet opened electrically by an
electro-magnet when coupled  to another manual.

But there is still something very satisfying in the workings of a traditionally built wood and leather stop action, and the life expectancy must be considerably more than the modern electrical counterpart, good as they are. From an organ builder's point of view, traditional actions are far less daunting to maintain. The modern solid state electronics and circuitry used in organs today can be complex indeed, and easily damaged by the unwary.

Fortunately, we do have clever people who specialize in, and build, these solid state actions. But then, should a mysterious fault occur and we ordinary chaps have to ask advice - to avoid Pooteresque blunderings - our "boffins" can quite bubble with enthusiasm and speak, alas bafflingly, of processor based capture systems, reversed polarities, diodes and memory chips, etc. Heads start to swim and eyeballs roll like marbles in a oothmug  - well mine do. But more often than not the fault can be traced, with their help, to a small section of the action requiring only a "plug-in" circuit board to be returned for repair which, when successfully replaced in the organ, makes the whole thing seem so easy. Thankfully on this occasion, for us and our organist and choirmaster with his wayward fifteenth, it proved more cost effective to re-leather and restore his present drawstop machine rather than replace it with a new electric system and, indeed, it's rewarding to know the machine will continue to work well for yet another lifetime.

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