The electric organ action
Introduction
Many pipe organs, from the very earliest right up to the present day, use an entirely mechanical system to sound the pipes in response to keys being pressed. In principle, such a 'tracker action' organ is very simple indeed. When you press a key, a system of linkages leading from the key to the windchest pulls open a valve called a pallet, which lets wind (lightly pressurised air) into the correct pipes for that note. When you pull a drawstop to 'turn on' a certain rank of pipes of a particular tone, another mechanical linkage moves a length of wood called a slider along under the 'feet' or wind inlets of those pipes. A row of holes in the slider lines up with the pipe feet allowing wind to flow through from the pallets below. When the stop is pushed in, the holes in the slider move out of line and the wind is shut off. What could be more straightforward? Bach composed splendid music for organs like this, and gave consummate performances on them with not a single electric circuit in sight. The wind, incidentally, was kept up by a couple of men working the bellows.
The challenge
People wanted more. Bigger organs with more stops, more manuals, more pipes, higher wind pressures. As the King of Instruments became yet more regal, the organist's work became yet more arduous. More stops meant more wind, hence bigger pallets and more effort required to press the keys to open them against the wind pressure. More manuals meant more trackers, more sliders, more moving parts by the thousand. With five manuals and pedals, 100 speaking stops and a few swells there would be over 440 independent linkages from console to windchests, each of which might have to negotiate many changes of direction. Now add the couplers, little mechanisms required in multiples of 61 to allow one manual to play the stops of another, all increasing the effort required at the keys. At some point, something would have to give; probably the organist's fingers.
The solution
As the size and specification of organs developed, the requirement for some kind of mechanisation became exponentially greater. The first relief arrived in the form of the 'Barker Lever' patented in 1839, a pneumatic power-assistance device to lighten the key touch. However this did nothing to overcome the mechanical inflexibility of the tracker action. By the latter half of the 19th century successful solutions were beginning to appear that offered not only lightness of touch and economy of moving parts, but also a tremendous scope for additional facilities. In the long run, three systems were successful in competing with the tracker action:
As electric and electropneumatic components became commonplace in action building, more applications were found for them enabling new aids to performance to be included in typical instrument specifications. Electromechanical controls make light work of implementing simple binary logic functions, and these offered a vista of new possibilites. For examples of the particular benefits offered by electric and electropneumatic actions, consider:
The sky was the limit and complexity soared. This was the age of electrification and there was magic in the very word itself.
The spin-off
One of the pioneers of electric action in the UK was Robert Hope-Jones, an electrical and telecommunications engineer-turned-organ-builder. Although his organ-building was not always up to the standard of his electrical contrivances, some of Hope-Jones' work was genuinely innovative and his legacy lives on: In collaboration with the Rudolph Wurlitzer company of New York, USA, he developed the 'Wurlitzer Hope-Jones Unit Orchestra', embodying many of his original ideas. This, folks, is the 'Mighty Wurlitzer' theatre organ, which is where we came in.
Watch this space
Six repaired relays
Soon, we will be revealing the myriad complexities of electric organ actions; Some are beautiful pieces of craftsmanship, others just assorted bent bits of tinplate lashed together with a rats-nest of wire. In the meantime take a look at these relays salvaged from a defunct Compton. When an organ builder wants a relay, it must often have not just one contact but sixty-one (one for every key on a manual), or perhaps one for every stop or piston; organ action is rather peculiar in this regard. These six 24-pole relays are connected in parallel to behave as one unit with 144 contacts, all normally-open and sharing a common terminal. This might have operated a function such as general cancel (turning off every stop at once), where many magnets normally isolated from one another must be connected to a supply when the relay is energised. These days many circuit arrangements of traditional electric organ action could be simplified by incorporating elementary diode logic, in this case using one contact and 144 diodes, but before silicon devices became cheap and reliable in the 1970s there was little option but to provide multiple contacts for anything more than the simplest task. Despite the intricacy of the circuits, many organ builders persisted in making electric action parts from the materials they had mastered for pneumatic actions; wood, felt, leather, etc. Others bought standardised electrical components from manufacturers such as Kimber Allen, whose logo can be seen on the bobbins of these relays. They are still unmistakeably organ relays, with their silver wire contacts, heel-end armature pivots and felt endstops. Compton have installed them in the traditional way by bolting them to the organ builder's equivalent of a pressed steel chassis: a piece of wood.
Organ links
Further reading
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