This invention relates to organ systems, and more particularly to a stop tablet control system for an organ for providing convenient visual indication of what stops are being played. 
Over the many years of organ development, a wide variety of systems for controlling organ stops have been devised, perhaps the earliest of which was a form of draw knob which, in the case of a pipe organ, required the exertion of considerable energy to accomplish the mechanical result necessary to achieve the desired stop effect.  Such draw knobs have in more recent times been electrified and provided with switches which are actuated by movement of the knobs to activate electrical or pneumatic systems for accomplishing the required mechanical work involved in setting the stops.  Another system now in common use is the so-called tablet control, which consists of a multiplicity of stop tablets pivotally supported above the keyboard of the organ and typically arranged to toggle between an up "off" position and an "on" down position.  Another type of system is the tilting tablet, used to some degree in pipe organs, and quite commonly on spinet electronic organs, which consists of a small tilting tablet, pivoted in the middle, which when the upper part is pushed turns on the stop and when the lower part is pushed the stop is turned off. 
In all of these systems the "on" and "off" condition of each stop is visually indicated by the mechanical position of the draw knob or stop tablet.  Although such systems have long been in use, indicating that their performance is generally satisfactory, they do have limitations, particularly when used with so-called "combination actions" in which many stops are changed en masse.  With combination actions, of which several types are known, pushing a single button called a piston automatically changes the registration of all of the stops (which sometimes number 100 or more) en masse, or at least all of the stops in a particular division of the organ.  Several preset combinations are stored in some form of temporary memory so that the organist can alter which stops are played in response to actuation of a given piston as requirements change from time to time.  Sometimes during a concert, the organist will find it desirable to change the combination between selections so that a given piston will give a particular tonal effect in one case and a different tonal effect, appropriate to another selection, in the other case.  Usually, however, the pistons in a church organ, of which typically there are six, ten or sixteen pistons per keyboard, would be set up in their most generally used combinations, but adapted to be changed from time to time. 
A drawback of combination actions, which has largely limited their use to large, expensive organ systems, is their cost.  Even the simple hard-wired combination system, in which the stops that are actuated by a given piston are pre-wired at the factory, and thus not subject to variation, require physical movement of several tablets, which is difficult to accomplish silently.  For example, if the toggle action of the tablets is designed to have a "positive" feel when operated manually, a multiplicity of tablets will offer considerable spring resistance that must be overcome by the motor mechanism that actuates the tablets, thus generating a certain amount of undesirable noise as they all toggle from one position to another.  Moreover, a large amount of power is required to operate combination actions of the kinds in current use.  If, for example, the stop tablets, in the combination action mode, are actuated by respective magnets, which may number as many as 200, and it is desired to move all 200 tablets from their "on" to their "off" position at the same time, a relatively large amount of power is required which, in turn, necessitates the provision of a large and expensive power supply.  Because of these costs and complications, low priced electronic organs are not equipped with combination actions.  Some available organs have a system of preset combinations wherein pushing a given piston button disables all of the conventional stop controls and substitutes some factory pre-wired combination.  Such organs normally have an indicator lamp installed somewhere on the organ which when illuminated tells the organist that he is not using the manual stops but is instead using a factory preset combination.  Unless the organist is totally familiar with the organ, he has no way of knowing which stops are on when a particular pre-wired combination is selected.  There is nothing to tell the organist that stops are being played, thereby making it difficult to manually "tailor" the combination should he decide that the stops being played are less than satisfactory for the selection he is playing.  Thus, it is evident that a non-indicating system, particularly in the case of combination actions, is very limited and leaves much to be desired. 
Although it is known to employ illuminated switches on electronic organs to indicate when a stop or stops are actuated, such systems suffered from the mechanical difficulties discussed above and lacked aesthetic appeal.  For example, in the early 1900's the Estey Company of Brattleboro, Vermont, manufactured what was known as the "cash register" organ which had an array of buttons having lamps therein that would be selectively illuminated upon momentary depression of a respective button to indicate that a given stop had been actuated.  A more recent application of the general concept of utilizing an energized lamp to indicate the actuation of a stop control device is in certain organ models manufactured by the Rodgers Organ Company in which draw knobs used for stop control have lamps mounted therein which are energized in response to operation of the draw knob of the "on" position and are extinguished when the draw knob is returned to its normal unoperated position. 
It is a primary object of the present invention to provide a true indicating combination action for an organ which overcomes the above-described problems of present systems.  Another object of the invention is to provide an indicating combination action that is silent in operation, is easy to manufacture and adjust, requires a minimum of power for its operation, and gives the organ a certain visual appeal.