US3463867A - Electronic organ keying system - Google Patents

Description

Aug. 26, 1969 L. w. PAVIA ELECTRONIC ORGAN KEYING SYSTEM Filed April 28, 1966 FIG.

MAX/MUM VOLUME M RA E P M w MN mm A A M V 4 E a L My 6 m$u3qw F w A m w Mo 0 ost a r n 265C w United States Patent US. Cl. 84-1.21 4 Claims ABSTRACT OF THE DISCLOSURE An electronic organ keying system is disclosed in which a plurality of conductive bus bars are used to connect individual tone generators through filters to a common amplifier and speaker system. The bus bars are tubular members of a conductive rubber and have both longitudinal and vertical resistances. Each key carries a plurality of electrical contacts, each of which depresses against one of the bus bars and makes electrical contact therewith so that the electrical resistance decreases as the key is depressed and the contact bears more firmly against the bus bar.

Each bus bar is individually scaled by displacing output contacts in relation to the key contacts so that different amounts of longitudinal resistance are encountered by the tones in traversing the bus bars and through the individual filters to the common amplifier.

In general, this invention relates to a new and improved electronic organ keying system and, more particularly, to a keying system for an electronic organ having continuously running oscillators, which system substantially eliminates transient sounds upon depression of the organ keys and, further, which is operative to scale the volume of the individual tone generators to meet the special requirements of each individual stop.

In electronic organs which have continuously running oscillators, the depression of an organ key connects the tone generator through predetermined stops and filters to an amplifier, and thence to the loud speaker of the organ for reproduction of the tone desired. However, there is no way to determine, upon depression of a key, whether the alternating current signal from the tone generator will be at a zero level, or a maximum level. .When the signal is at a maximum level, the depression of the key creates an undesirable click or pop which detracts from the desired musical effect. To eliminate these clicks and pops, the prior art has utilized rubber switching contacts associated with the individual keys. However, it has been difiicult to achieve with these solid rubber contact members a slow attack necessary to minimize the clicking sounds. These rubber switching contacts have wires running the full length of the bus bar. Further, a slow attack is essentially similar to the effect achieved with a pipe organ in that there is, normally, an initial period after depression of the keys on a pipe organ before the full volume of any pipe has been reached.

An additional problem relating to the keying of individual notes has been the relative volume of the individual tone generators. Thus, the lower notes often had a higher volume than the higher notes, or vice versa, or all of the notes were of an even volume.

The generators used in this invention initially have uniform electrical outputs. In order to achieve the individual tonal characteristics required for specific stops it is necessary to filter the basic signal. Filtering results in uneven scaling. When a high pass filter is used, the lower notes of the scale are weak in volume. By connecting the bus bar utilized in the present invention at its lower end to the filter the weaker lower notes encounter less horizontal resistance than the upper stronger notes which must pass 3,463,867 Patented Aug. 26, 1969 through a greater resistive barrier to reach the filter. It is this compensating factor that allows a uniform volume level where normally the filter would tend to strengthen the upper notes and weaken the lower. The reverse is true for low pass filters. A further advantage of this invention is that an electrical output may be taken at any point on the bus bar resulting in a specific reinforcement of any desired portion of the scale. Each bus bar works on a specific pitch i.e. 16, 8, 4, etc. Any number of filters may be connected to one bus bar all having the same footage. Some of these'filters may be high pass and some low pass and they individually will take their outputs from that portion of the bus bar required to achieve even scaling.

Therefore, it is the general object of this invention to avoid and overcome the foregoing and other difliculties of prior art practices by the provision of a new and better electronic organ keying system.

Another object of this invention is the provision of a new and better electronic organ keying system for electronic organs having constantly energized tone generators in which clicks and pops which would normally occur with the depression of the organ keys are kept to a minimum.

Still another object of this invention is the provision of a new and better electronic organ keying system in which the tones produced by depression of the keys have a slow attack in order to reproduce the sound produced by pipe organs.

A further object of this invention is the provision of a new and better electronic organ keying system which achieves scaling of the tone generators for each of the stops without any need for special complicated and expensive circuitry.

Other objects will appear hereinafter.

For the purpose of illustrating the invention, there is shown in the drawings a form which is presently preferred; it being understood, however, that this invention is not limited to the precise arrangements and instrumentalities shown.

FIGURE 1 is a cross-sectional view of a bus bar and key actuated depressors built in accordance with the teachings of the present invention.

FIGURE 2 is a side elevational View of the key operative to control any one of a plurality of bus bars.

FIGURE 3 is a graphical showing of the sound produced by the depression of a particular key built in accordance with the principles of the present invention.

FIGURE 4 is a schematic showing of the keying system of the present invention utilized in an electronic organ.

In FIGURE 1, there is shown a bus bar and associated depressors utilizing the teachings of the present invention. The bus bar 10 is a conductive rubber tube having a hollow core with no wire running through the hollow core and is manufactured of a conductive rubber whose resistance decreases with compression thereof. Along the length of the conductive rubber tube 10 there are positioned a plurality of depressors 12, 12a, 12b, 12c, 12d, 12c, 121, 12g, 12h. Each of the depressors 12-12h are associated with a particular key of the keyboard. Although only nine depressors have been shown, it will be understood that the bus bar 10 will be of a length sufficient for the normal use wherein the depressors are equal in number to the number of keys on the keyboard. The bus bar 10 is suspended from insulating supports 14 positioned as required. The conductive rubber bus bar 10 has connected thereto two wires 16 and 18. Wire 16 is connected at one end of the bus bar 10, whereas wire 18 is connected at the other end thereof. It will be understood for the purposes of this invention that the bus bar 10 can be manufactured of any material having a resistance which decreases with compression thereof and, further, which is resilient so that it will return to its original shape when its associated key is released to its initial position.

As shown in FIGURE 1, the depressors 12-12h are adapted to compress a small portion of the surface of the bus bar 10. Each of the depressors 12 is a conductive member adapted to complete a circuit between a tone generator connected to the depressor 12 and one of the wires 16 or 18. The depressor 12d is shown achieving only light contact with the bus bar 10. The depressor 12e is shown with a firmer contact with the bus bar 10. It will be under stood that the conductivity of the bus bar increases with firmer contact thereon. Additionally, and importantly, the resistance between the tone generator connected to a depressor 12-12h and the ultimate speaker will depend upon the resistance between any particular depressor 12-12h and one of the wires 16 or 18. Since the bus bar 10 has a uniform resistance per unit length, and the distance between wire 16 and depressor 12 is much shorter than the distance between depressor 12 and wire 18, therefore, the resistance between wire 16 and depressor 12 is much less than the resistance between wire 18 and depressor 12. Accordingly, the output signal at wire 16 will be much greater than the output signal at wire 18 because of this lower resistance. However, this will vary in accordance with the distance between the individual depressors 12-12h and the closest wire 16 or 18. It can be seen that by judicious placement of the wires 16 and 18, a scaling of the resistance between the closest wire to a particular depressor can be achieved. In this way, for a particular bus bar 10, a particular scaling of the output volume with respect to each one of the depressors 12-12h can be effected in a simple and easy manner. Further, this scaling is achieved without the need for any special circuitry. For example, if the input wire 16 were removed and only the input wire 18 were utilized, the resistance between any particular depressor 12-12h and the output wire 18 would vary linearly in accordance with their position from the end of the bus bar 10 connected to the wire 18.

If wire 18 was disconnected and only wire 16 utilized, it will be obvious that the output volume achieved when depressor 12a is depressed is far greater than will occur when depressor 12h is depressed. Those depressors closest to output wire 16 will of course have their volume enhanced while those depressors further away from wire 16 will have their output volume decreased because of the increased resistance along bus bar 10.

All other compressible material bus bar systems have vertical resistance only. It is a unique feature of this invention that its bus bar is of a compressible material which had both a vertical and a horizontal resistance which permits the elimination of undesirable clicks and pops and also provides exact control of scaling.

The bus bar 10 and the depressors 12-12h are adapted to be utilized in an organ system in which the tone generators are always on. Thus, when a key is depressed, there is no way of determining whether the alternating current signal from a particular tone generator is at the point in the alternating current cycle when it passes through zero. If the alternating current signal from a particular tone generator is not passing through zero, then, normally a click will be heard. In order to eliminate this click or pop, the bus bar 10 has been manufactured of an elastic material which is rendered even more elastic by reason of its hollow construction. When the depressor 12 first touches the bus bar 10 it transfers its associated tone generator signal on to the bus bar. At this point, a transient click will occur. However, due to the high resistance of the conductive material at the initial depression, the click will be inaudible at the speaker. This is best shown in FIGURE 3 wherein the first cycle of an alternating current signal from the tone generator is shown as having a very small amplitude so that even though the signal is not passing through zero, at time zero, the signal is of such a small value that it cannot be heard. When a key presses its associated depressor down further into the bus bar 10, the resistance drops and, accordingly, the amplitude of the signal increases as shown in FIGURE 3 until it reaches its maximum volume. Thus, within a few cycles, the tone is heard, without any audible click or pop. This build up time to the actual volume of the signal gives the same speech characteristic as that of a pipe in a pipe organ being brought into play.

In FIGURE 2, there is shown a key 20 utilized to operate depressor 12 shown in FIGURE 1. The key 20 is pivotally mounted, in a standard manner and has connected thereto a rod 22 having pins 24, 26, 28, 30, 32, 36, and 38 associated therewith. The pins 24-38 are adapted to control the movement of depressors 12, 40, 42, 44, 46, 48, 50, and 52 respectively. Each one of the depressors 40-52 is positioned above a conductive rubber tubular bus bar 54-66 in the same manner as depressor 12 is positioned above bus bar 10. Similarly, it will be understood that on a given keyboard there are provided a plurality of keys each associated with depressors 12a-12h. Each of these keys is also associated with a plurality of depressors operative through a single actuator bar similar to actuator bar 22.

The depressors 12, 40-52, are each respectively connected to an isolating resistor 68, 70, 72, 74, 76, 78, 80, and 82. Each one of the bus bars 10, 54-66 is sealed in accordance with a particular pitch associated therewith, for example, bus bar 10 is scaled to be operative with a one-foot pipe stop tab; bus bar 54 with one and one-third foot pipe stop tab; bus bar 56 with a two-foot pipe stop tab; bus bar 58 with a two and two-thirds foot pipe stop tab; bus bar 60 with a four foot pipe stop tab; bus bar 62 with a five and one-third foot pipe stop tab; bus bar 64 with an eight foot pipe stop tab; and bus bar 66 with a sixteen foot pipe stop tab. Although eight bus bars have been shown, it will be understood that any number of bus bars could be provided for each manual of the electronic organ.

In FIGURE 4, there is shown a portion of an electronic organ 86 built in accordance with the principles of the present invention. The organ 86 includes a plurality of tone generators 88 each operative to produce a particular tone and each connected to a respective key 20 as shown in FIGURE 2. Only one bus bar 10 is shown in FIGURE 4, it being understood that each of the bus bars 10, 54-56 are similar in operation, and that the operation can be understood from a description of the operation of bus bar 10. Each of the bus bars 10 has its tap wires 16 and 18 connected to filters 90 associated with the bus bar 10. The filters 90 are controlled by stop tabs 92 which also control whether an output signal will be transmitted from a particular wire 16 or 18. Only the bus bar having its signals passing through the filters 90 to the output amplifier 94 will be heard and all of the other bus bars will remain silent. The amplifier 94 is connected to a speaker system shown schematically at 96. Each bus bar, has its own taps 16, 18 connected to its own filter and stop tabs which in turn are connected to the common amplifier 94. Thus each bus bar has its own individual filters and stops separate and apart from every other bus bar on the same manual or other manuals. It can thus be seen that with respect to each particular stop tab, the bus bar can be individually scaled without the necessity for special circuitry as the only requirement is the prepositioning of a particular tap 16 or 18 along the length of the bus bar 16.

Accordingly, the scaling of the tones has been made possible by tapping the rubber conductive bus bars at various points along its length and feeding these tones to particular filters and into the common amplifier. This process has been effected due to the fact that the tapping has varied the length of travel along the conductive bus bar placing more or less resistance between a particular signal input and the filters and amplifier.

The present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof and, accordingly, reference should be made to the appended claims rather than to the foregoing specification as indicating the scope of the invention.

I claim in my invention:

1. An electronic musical instrument comprising a keyboard having a plurality of keys arranged along the length thereof, each of said keys having a plurality of electrical contacts associated therewith,

a plurality of tone generators, each of said electrical key contacts being connected to one of said tone generators,

a. plurality of electrically conductive bus bars, each of said bus bars being electrically conductive along the length thereof and having its resistance decreasing with compression thereon, each of said keys being operative to cause its associated electrical contacts to come into contact with and to compress said bus bars,

electrical-acoustic transducer means, and output circuitry for connecting said bus bars to said transducer means for connecting the tones of said tone generators along the lentgh of said bus bars to said trans ducer means, said output circuitry including a plurality of output contacts for each of said bus bars said output contacts being spaced along said bus bars longitudinally with respect to the electrical key contacts of each of said bus bars so as to scale each said bus bar individually to attain ditferent tonal characteristics due to different amounts of the inherent longitudinal resistance of a bus bar being included between a key contact and an output contact.

2. An electronic musical instrument in accordance with claim 1 further including switching means for selectively connecting and disconnecting said output contacts to said transducer means for each said bus bar.

3. An electronic musical instrument in accordance with claim 2 wherein each of said bus bars is a tubular member of conductive rubber.

4. An electronic musical instrument in accordance with claim 1 wherein said output circuitry includes a common amplifier and individual filter means connecting each said output contact for each said bus bar to said common amplifier.

References Cited UNITED STATES PATENTS 8/1958 Lester 841.26 X 4/1960 Henley 338-6'9 US. Cl. X.R.

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