US3435123A

US3435123A - Electrical musical instrument keying system

Info

Publication number: US3435123A
Application number: US458257A
Authority: US
Inventors: Ray B Schrecongost
Original assignee: Hammond Corp
Current assignee: Marmon Co
Priority date: 1965-05-24
Filing date: 1965-05-24
Publication date: 1969-03-25
Anticipated expiration: 1986-03-25
Also published as: GB1133140A; DE1497856A1

Description

Miilch 25, 1969 R. B. scHREcoNGosT 3,435,123

l ELECTRICAL MUSICAL INSTRUMENT KEYING SYSTEM .filed may 24, 1965 sheet of 2 March 25, 1969 R. B. scHREcoNGos-r 3,435,123

ELECTRICAL MUSICAL INSTRUMENT KEYING SYSTEM Filed May 24, 1965 sheet 2 of 2 VOL T465' N `20V 20H5 /ams 'sa'.

50,445 -r/ME fppeox//wz rs) United States Patent O U.S. Cl. 84-1.26 6 Claims ABSTRACT F THE DISCLOSURE An electrical musical instrument keying system which provides double diode keyers for each signal source to be keyed. All keyers are normally held off by a common bias voltage which is variable, and are turned on individually by a keyed counter voltage which overcomes the bias voltage for the particular keyer. RC timing circuits are used to control decay subsequent to disconnection of the keying voltage source. Decay rate is variable depending upon the selected level of the common bias voltage. Variations in the basic system include provision of a dual slope decay envelope by the addition of a resistor and Vdiode connection in the RC timing circuit and the provision of two types of percussion by the incorporation of RC and diode connections in the keying circuits.

This invention relates generally to electrical musical instruments such as electric organs and similar toneproducing devices, and is more particularly related to apparatus for controlling the decay rates of musical tones produced by such instruments. The invention is concerned more specifically with controlling the operation of keying circuits employed in electric organs or other key-actuated electrical musical instruments whereby the rate of change in amplitude of tone signals may be controlled so that the sounds produced by such signals may be made to decay from their maximum strength at predetermined rates within the control of the player. By means of the invention, therefore, a variety of pleasing and interesting tonal elfects may be produced affecting the mood of the music being played and subject to selection by the player.

Although electric organs have previously been made wherein the rate of decay of the notes played was subject to a certain amount of control by the player, so far as I am aware such devices have been limited for the most part to systems requiring a large number of expensive electrical components and complex switches, and thus were not economically suitable for many commercial uses.

It is therefore a broad object of this invention to provide simple and inexpensive apparatus for use with electrical tone-producing instruments which permits control by the player over the rate of decay of notes played by the instrument.

It is a further object of the invention to provide apparatus of the type -mentioned in the foregoing object which is capable of selectively providing long and medium sustain and substantially instantaneous stop playing by adjusting one voltage in a system of many keyers used in the instrument.

A further object of the invention is to provide means for controlling the potential at a terminal in a keyer used in an electrical organ system wherein the keyer is connected between a tone signal source and the organ output system, and wherein the keyer is capable of changing the amplitude characteristics of the signal supplied to the output system depending on the potential applied to such terminal in the keyer.

Other objects, advantages, and features of this invention will be apparent from or pointed out in the following specification considered in connection with the accompanying drawings showing a preferred embodiment of the invention. In the drawings, wherein like numerals refer to the same or similar parts in the several figures:

FIG. 1 is a diagrammatic representation of a keying system of a keyer-operated electrical musical instrument, including a preferred form of keyer and showing preferred means in accordance with the present invention for controlling the rate of decay of electrical signals transmitted by the keyer to its output conductor;

FIG. 2 is a more general diagrammatic represenation of a keying system of an electrical musical instrument illustrating the use of a multiplicity of keyers of the type shown in FIG. 1 and the manner in which the decay rates of electrical signals transmitted by such independent keyers are controlled as a group by a single control means in accordance with the present invention;

FIGS. 3, 4, and 5 are diagrams illustrating the rate of change in the decay characteristics of electrical tone signals supplied by a keyer of the type shown in FIG. 1 to its output conductor, under several modes of operation.

FIG. 6 is a diagram of a network adapted to be substituted for a component of the system shown in FIG. 1, for improving the performance 0f the system;

FIG. 7 is a diagram comparing the decay characteristics illustrated in FIG. 5 with the `decay characteristics of electrical tone signals supplied to the Output system fby a keyer modified by inclusion of the network of FIG. 6, under two modes of operation;

FIGS. 8 and 9 are diagrams showing networks which may be substituted for a component of the system shown in FIG. 1, for providing different modes of operation of the system.

Referring now particularly to FIG. l, the invention is there diagrammatically illustrated as incorporated in the circuit of an electric organ of the type in common use wherein an individual tone signal source is provided for each of the audio-frequency signals corresponding to the notes within the range of the instrument. Such tone signal sources may be of any suitable type, such as electronic oscillators, with or without associated frequency dividers, for instance. In the embodiment shown in the drawing it will be considered, in the interest of being specic, that the invention is applied to a single manual keyboard having electronic generators as the source of the audiofrequency signals. It will, of course, be understood that the invention is applicable to more than one organ keyboard, including, if desired, a pedal keyboard.

In FIG. 1 there is shown a tone signal source 10, such as an electronic oscillator, coupled through a lead 12 to a keyer shown enclosed in a box and indicated generally at 14. The keyer 14 includes a high impedance element or resistor R16 in series with a 'resistor R18 of lower resistance, the common connection 20 of these resistors being connected by a lead 22 to one side of a diode 24. The remote end of the resistor R16 is connected to the lead 12, and the remote end of the resistor R18 is connected by a lead 26 to a common lead 28 connected to a source of low, preferably negative, potential, for example 0.15 volt. In series with the diode 24 is a second diode 30, the other side of which in turn is connected through an output conductor 32, containing a resistor R34, to a common lead 36 to the output system of the instrument, the lead 36 being grounded through an impedance element such as a resistor R37. The output system of the instrument is not shown since it does not constitute part of the present invention, but it may be of conventional design including electroacoustical translating means for translating into sound the signals supplied to the lead 36.

Also connected to the common lead 36 are a plurality of other resistors, such as R34', R34", and R34 corresponding respectively to the resistor R34 and illustrative of such resistors in all of the other keyers in the organ system. The

diodes

24 and 30 are disposed back-to-'back and are oriented in the circuit to pass direct current outwardly from a common terminal 38 between them, and each diode becomes conductive to an alternating current signal when the potential on the terminal 38 exceeds the extinction potential of the diode. The

diodes

24 and 30 thus constitute a variable impedance signal transmission device which is normally non-conductive, but which becomes conductive when the potential at the terminal 38 exceeds the extinction potential of the diodes. Accordingly, the amplitude characteristics of the tone signal transmitted through the diodes to the instrument output system are dependent upon the potential applied to the terminal 38. In the embodiment being described, the

diodes

24 and 30 have equal extinction potentials of 0.6 volt. Diodes suitable for this purpose are the typical silicon junction diodes of commerce.

The terminal 38 is connected through a resistor R40 of high resistance and a resistor R42 of low resistance, in series, and through a lead 44 to a switch 46 by which the keyer may be connected to a common lead 48 connected to a source of positive potential; for example, -I-3 volts. The switch,y 46 is adapted to be operated by a playing key (not shown) of the organ in well known manner; that is, the pressing or actuating of the associated playing key closes the switch 46, whereby the potential at the termin-a1 38 is raised above the extinction potential of the

diodes

24 and 30, rendering them conductive, and thus conditioning the keyer to transmit to the organ output system a signal corresponding to that provided by the signal source 10. Conversely, releasing such playing key opens the switch 46, causing the potential at the terminal 38 to drop below the extinction potential of the diodes, rendering them non-conductive, whereby passage of such signal to the organ output system is discontinued, as will be more fully described hereinafter.

The junction or common connection 50 to resistors R40 and R42 is connected through a capacitor C52 to a source of bias potential below the extinction potential of the

diodes

24 and 30, such as ground. The junction 50 is also connected through a resistor R54 of high resistance and a lead 56 to a common lead 58 connected to the blade 60 of a step switch 62 having a plurality of terminals, here shown as three, i.e.,

terminals

64, 66, and 68, connected respectively to sources of different potential each of which potentials is lower than the aforementioned extinction potential, but none of which is higher than that of the said bias potential sour-ce connected to the capacitor C52. The sources of potential connected to the

said terminals

64, 66, and 68, may be, for example, -20 volts, -3 volts, and ground potential. Also connected to the common lead 58 are a plurality of other resistors, such as R54', R54, and R54'", corresponding respectively to the resistor R54 and illustrative of such resistors in all of the other keyers in the organ system.

Referring to FIG. 2, there is illustrated diagrammatically an organ keying system employing a plurality of keyers identical to those previously described and shown in FIG. 1, FIG. 2 also showing the manner in which the keyers are incorporated in the main organ circuit. In FIG. 2 the reference numerals for the various parts are the same as those used for similar parts in FIGA, with differentiating suiixes a, b, and n to denote groups of assocaited parts, to facilitate the description.

The outputs of the audio-frequency signal generators a, 10b, and 10n are coupled respectively through their associated leads 12a, 12b, and 12n to keyers 14a, 14b, and 14n identical to the keyer 14 previously descri-bed. Although only three keyers are shown for purposes of illustration in FIG. 2, it is to be understood that the number of such keyers used in the organ system depends upon the number of playing keys in the instrument which have the invention applied thereto.

The keyers 14a to 14n are also connected respectively through their associated leads 26a to 26n to the common .15 v. lead 28, through their associated leads 44a to 44n to the playing key switches 46a to 46n, and through their associated leads 56a to 56n to the common control lead 58. The keyers 14a to 14n are likewise connected through their respective associated output conductors 32a to 32a to the common lead 36 connected to the instrument output system.

In an organ system in which the amplitude of the signals supplied to the keyers is about 1.5 volts and the potentials supplied to the lines `28, 48, and 58 are =as indicated above, I have found that good results are obtained when the components of the keyers have the following values, wherein the resistances of the resistors are in ohms (K representing 1000):

Component: Value R16 47K R18 4700 R34, R34', R34 2200 R37 1000 R40 33K R42 100 RS4, R54', R54", R54 100K C52 microfarads 20 Operation of the present apparatus will now be described With particular reference to FIG. 1, in which description it will be assumed that the values of the various components and the potentials supplied to the

lines

28, 48, and 58 are as described above. When the electric organ is turned on, the tone signal sources supply their respective tone signals at constant amplitude to their associated keyers, and therefore the signal supplied by the source 10 is impressed on the lead 22 of the keyer 14. Assuming the amplitude of the signal supplied to the input lead 12 to the keyer to be about 1.5 volts as mentioned above, the signal potential on the lead 22 will be about millivolts, peak to peak.

Assuming further that the switch arm 60 is in contact with the terminal 68 to ground, if the player now actuates the playing key associated with switch 46, thereby closing said switch, a potential of about '0.7 to 0.8 volt is impressed on the terminal 38 from the line 48, capacitor C52 becoming charged at the same time. Since the potential at the terminal 38 thus exceeds the 0.6 Volt extinction potential of the

diodes

24 and 30, the diodes become conductive, and the tone signal passes through the diodes to the output conductor 32, and thence to the output system of the instrument. Transmission of such signal to the output system of the instrument continues at a constant amplitude as long as the switch 46 is closed, i.e., as long as the associated playing key isl pressed. Releasing the playing key causes the switch 46 to open, whereupon the capacitor C52 discharges principally through the resistor R54, some discharge also taking place through R34, R37 and R18. The signal continues to pass through the

diodes

24 and 30 to the output system on a declining basis until the potential at terminal 38 drops to the extinction potential of the diodes, at which time the diodes become nonconductive and transmission of the signal to the output system ceases. The amplitude of such output signal is therefore progressively reduced, and the sound produced therefrom by the output system correspondingly decays as the capacitor C52 discharges. Because of the negative bias imposed on the lead 22 by its connection through lead 26 to the line 28, diode 24 becomes conductive slightly before diode 30 when switch 46 is closed, and extinguishes slightly after diode 30 when capacitor C52 discharges after switch 46 is opened, this mode of operation providing a better decay envelope of the signal passing to the output conductor 32 than would be obtained if the

diodes

24 and 30 simultaneously became conductive and then simultaneously extinguished. With the common lead 58 connected to the ground terminal 68 of the step switch 62, the decay from maximum voltage to the extinction potential of the diode 30 takes about three seconds. This is illustrated in FIG. 3, which shows the relation of voltage at the capacitor C52 to time, following opening of the switch 46, the potential at the capacitor decaying exponentially and rather gradually from the maximum of about three volts to ground potential.

If, in operation of the keying system, the arm 60 of the switch 62 engages terminal 66 (-3 volts potential), the decay rate is considerably faster than that just described, the decay from maximum potential to the extinction potential of the diode 30 here taking about one second. This is illustrated in FIG. 4. FIG. 5 illustrates the much faster decay rate obtained when the arm 60 is engaged with the terminal 64 (-.20 volts potential) of the step switch, the decay period in this instance being about 100 milliseconds. The moment at which transmission of the signals to the output system ceases is the point shown in FIGS. 3, 4, and 5 at which the curve crosses the horizontal line representing the 0.6 volt extinction potential of the diode 30.

If a more rapid decay rate is desired, but it is desired not to exceed -20 v. as a connection for the lead 56, on the ground that this might produce an excessive reversing voltage through the switch 62 during the periodic increase and reduction in potential at the terminal 38, this can be accomplished by applying a lower voltage, eg., +1.5 v. instead of +3 v., to the bus 48. This of course reduces the initial signal voltage at the output conductor 32, requiring the output signal to be ampliiied to a greater degree than is necessary when the bus 48 carries 3 volts. Such additional amplification is of course easily accomplished by means well known in the art.

An improved decay envelope shape over that achieved through the use of the simple resistor RS4 in the lead 56 may be obtained by substituting a diode-resistor network therefor, one form of which is shown in FIG. 6. Referring to FIG. 6, it will be seen that the network comprises a resistor R70 connected at one end to the junction 50 and at the other end to the common lead 58. Bypassing the resistor R70 is a second resistor R72 connected in series with a silicon diode 74 oriented to be conductive when the potential is higher at the junction 50. When this network replaces resistor R54 having a resistance of 100K, the resistors R70 and R72 preferably have resistances of 220K and 100K, respectively.

Reference is now made to FIG. 7 which graphically depicts the rate of potential drop at the junction 38, and the decay characteristics of the tone signals passing through diode 30 to the output conductor under various conditions during discharge of the capacitor C52. As in FIGS. 3 to 5, the moment when transmission of the respective signals to the output system ceases is shown in FIG. 7 by the intersections of the curves with the horizontal line representing the 0.6 volt extinction potential of the diode 30. In FIG. 7 all of the curves represent the above-mentioned rate of potential drop and the signal decay characteristics produced by having the mode switch blade 60 in contact with terminal 64 connected to the -20 v. potential source. Curve x represents the decay characteristics observed when the energizing voltage from the bus l48 is +3 volts and the simple resistor R54 is present in the lead 56 for discharging the capacitor C52, and shows that the potential on the terminal 38 decays to the extinction potential of diode 30 (0.6 volt) in about 100 milliseconds. Curve y depicts the decay characteristics of the signal under conditions similar to those for curve x, except that the resistor R54 has been replaced by the resistor-diode network of FIG. 6, and shows that the potential on terminal 38 decays to the extinction potential of diodes 24-30 in about 5,0 milliseconds, most of this decay occurring rather quickly. Curve z depicts the decay characteristics of the signal under conditions similar to those for curve y, except that the energizing voltage supplied by bus 48 is +1.5 volts and shows that the potential on terminal 38 decays quickly to the extinction potential of diodes 24-30 in about 20 milliseconds. The decay envelope of the signal improves, it is believed, resulting in a more pleasing musical effect, as the curves drop more vertically initially.

The improved effects obtained by using the resistordiode network of FIG. `6, as just described, may also be obtained by using a non-linear resistor, such as a silicon carbide resistor in place of resistor R54.

In the foregoing description, the invention has been described as used in conjunction with keying providing sustained playing of a note as long as a key-operated switch is closed. It will of course be understood that the invention is also applicable to keying systems providing other modes of operation, such as percussion, or percussion-sustain systems. Modications of the keyer of FIG. l, adapting the keyer for such percussion and percussionsustain operation, are shown respectively in FIGS. 8 and 9 and are representative of other forms of keyers with which the present invention may be used.

In FIG. 8 the terminal 38 between

diodes

24 and 30 is connected through the resistor R40 to the junction 50 which is connected through the resistor R54 to the mode switch `62, as described above. In the embodiment here described, however, the junction 50 is connected to ground through a capacitor C76, and is also connected through a resistor 'R78 to a common connection to a capacitor C80 and one side of a diode 82, the other side of the latter being connected to ground. The diode is oriented to be conductive when the common point between C and R78 is sufficiently below ground. The capacitor C80 is connected through a resistor R84 to a 3 volt D.C. terminal of the power supply, and the common connection to capacitor C80 and resistor R84 is connected through a keyoperated switch 86 to ground. The other components of the keyer, and its connections to the signal source, the output system, the mode switch 62 and the common lead 28, are all the same as in FIG. l previously described. Suitable values for the added components of the embodiment of FIG. 8 are: 1000 ohms for the resistors R78 and R84, .47 microfarad for capacitor C76, and 20 microfarads for the capacitor C80.

In operation ofthe embodiment of FIG. 8, upon closing the switch 86 by pressing the playing key associated therewith, the capacitors C76 and C80 become positively charged, and the potential at the terminal 38 is raised above the +0.\6 volt extinction potential of the

diodes

24 and 30, whereupon the signal supplied by the signal source 10 passes through the

diodes

24 and 30 to the output system of the instrument. The capacitors C76 and C80, which have divided the initial charge on C80, immediately begin to discharge, lowering the potential of the terminal 38, and the transmission of the signal to the output system stops when the potential at terminal 38 drops to the extinction potential of the diode 30, as described above. Note that this effect is due to the initial charge on C80 which is divided with C76. If the key is held long enough, the decay cycle is automatically completed. If the key is released before completion of the decay cycle, the note is extinguished by reestablishment of the -3 v. connection to the capacitor C80.

FIG. 9 is substantially the same as FIG. 8, except that in the former the junction 50 is grounded through a capacitor C88 and a diode 90 is disposed between the resistor R78 and the common connection to the capacitor C80 and the diode 82. Diode 90 is oriented to pass current toward the junction 50. A suitable value for the capacitor C88 is 20 microfarads, and the other capacitors and resistors in FIG. 9 have the values given above. Operation of the modification of FIG. 9 is similar to that of the modification of FIG. 8, except that if the key contact 86 is opened before completion of the potential rundown at the junction 38, capacitor C88 continues to be eiiective, even though capacitor C80 is discharged. The note is not immediately extinguished, therefore, as in FIG. 8, but trails off at a more rapid rate than prior to key release.

In all of the embodiments of FIGS. 1, l8, and 9, it is seen that decay of the signal commences upon the cessation of conduction of charging current to the capacitor or capacitors in the respective keyers. In FIG. l such cessation of charging current is brought about by release of the playing key, which causes switch 46 to open, whereas in FIGS. 8 and 9 the cessation of charging current occurs immediately after the key-operated switch -86 is closed.

Operation of the general keying system used in playing notes of all frequencies vvithin the range of the instrument will be apparent from FIG. 2. Since the keyers 14a to 14n have parallel connections to the leads 28, 36, and 8, and (through switches 46a to `4611) to the lead 48, any number of notes may be played simultaneously by actuating or pressing the playing keys corresponding thereto, which in turn will close respective associated ones of switches y46a to 46u, and each note will decay at the rate established by the position (selected by the player) of the arm 60 of the step switch 62 when the playing key associated with such note is released (FIG. l), or played (FIG. `8), or played and released (FIG. 9), in the manner described above. Thus, the present invention provides simple apparatus whereby the player can select any one of a plurality of decay rates for signals supplied to the output system by all the keyers in the musical instrument simply by manipulating a single switching member, this control feature being one of the important advantages of the invention.

A further advantage of my invention is that it permits the use of operating voltages (i.e., the voltages impressed on the terminal 38) which are high relative to the voltage of the tone signal input at the diode 24, 'whereby distortion of the wave form of the signal during the decay interval may be maintained below the limit of perceptibility to the ear.

While I have shown and described a particular embodiment of my invention, it will be apparent to those skilled in the art that numerous -modications and variations may be made in the form rand construction thereof, without departing from the spirit and scope of the invention. For example, it will be understood that the extinction potentials of the diodes need not be as given, and that they may be higher or lower than the above mentioned value of 0.6 volt, and may even have negative values. Likewise, the values of the various components of the keyers, and values and signs of the potentials supplied to the lines 28, '48, and S8, are not critical and may be varied, if desired. Such values are all a matter of choice, and one skilled in the `art will readily understand how variations therein will aiiect the operating characteristics of the keying system. It will also be apparent that the invention is not limited to use with the specific keyer described herein, but may be used with other kinds of keyers, such as transistor keyers, tube keyers or keyers containing other solid state devices, in which transmission of a signal through the keyer is dependent on the potential at a given point or terminal therein. I therefore desire, by the following claims,

to include within the scope of my invention all such modiiied forms of the apparatus disclosed herein by which substantially the results of the invention may be obtained by substantially the same or equivalent means.

I claim:

1. A keying system for an electrical musical instrument having a plurality of tone signal sources covering a musical range of several octaves, a common output system, and a plurality of keyers individually connecting the sources to the output system, said keyers individually cornprising a pair of diodes in series connected between each source and the output system, said diodes being oriented to pass direct current outwardly from a terminal between them, a plurality of DC bias sources all below the extinction potential of said diodes, a bias lead common to all of said keyers, switch means for connecting any selected one of said bias potential sources to said common bias lead to fix the extinction bias thereon, a timing capacitor for each of said keyers connected to said bias lead, each of the capacitor bias connections including an impedance element, za source of keying voltage above the extinction potential of said diodes, an actuating circuit including a playing `key operated switch and an impedance element connected for applying the keying voltage to said timing capacitor by way of the last said impedance element in opposition to the selected bias voltage on said capacitor when said playing key switch is operated, a circuit connecting the terminal between said diodes to said timing capacitor, the last said circuit including an impedance element, :and the value of the capacitor bias impedance element being high as compared with the value of the keying voltage impedance element.

2. The keying system as called for in claim 1 in 'which all of the impedance elements are resistors.

3. The keying system Ias called for in claim 1 in which the capacitor bias impedance element is a resistor in parallel with a series connected resistor and diode.

4. The keying system as called for in claim 1 in which the :keying voltage source is a capacitor, means for charging said capacitor and means including said playin-g key switch providing a connection for transferring a portion of the change on the last said capacitor to said timing capacitor when said playing key switch is operated.

5. The keying system as called for in claim 4 in which the connection for transferring charge from the voltage source capacitor to the timing capacitor includes means for preventing transfer of charge in the reverse direction.

6. The Ikeying system as called for in claim 5 in which the means for preventing reverse transfer of charge is a diode.

References Cited UNITED STATES PATENTS 3,196,201 7/1965 McDonald 84-1.26 3,333,042 7/1967 Brombaugh SLi- 1.26

ARTHUR GAUSS, Primary Examiner.

vROBERT H. PLOTKIN, Assistant Examiner.

U.S. C1. X.R. 84-1.l3