US3558792A

US3558792A - Electronic organ circuit for simulating guitar

Info

Publication number: US3558792A
Application number: US756558A
Authority: US
Inventors: Alberto E Kniepkamp
Original assignee: Chicago Musical Instrument Co
Current assignee: Lowrey Industries Inc; Chicago Musical Instrument Co
Priority date: 1968-08-30
Filing date: 1968-08-30
Publication date: 1971-01-26
Anticipated expiration: 1988-01-26

Abstract

A monophonic or a polyphonic set of organ pedal key-switches are connected to control electrical signals from tone signal sources, and to direct the tone signals through a filter which passes fundamental bass frequencies, the filter being connected through an amplifier to a speaker. Each key switch is arranged to operate a pedal-cancel circuit for terminating any previously played sustained note that is still sounding. A transistor switch and discharge capacitor are provided which are controlled by the keyswitches through the pedal cancel circuit for transferring selected electrical signals to a second filter which passes somewhat higher frequencies, especially the second harmonic, to the same or similar amplifier and speaker. The duration of the signals passing through the second filter is short and is thus electrically or acoustically superimposed on the fundamental signal, thereby simulating the percussive sound of a guitar, especially a bass guitar.

Description

United States Patent lnventor Appl. No.

Filed Patented Assignee Alberto E. Kniepkamp Chicago, 111.

Aug. 30, 1968 Jan. 26, 1971 Chicago Musical Instrument Co.

Lincolnwood, 111. a corporation of Delaware ELECTRONIC ORGAN CIRCUIT FOR 3,340,344 9/1967 Schwartzet al 5/1963 Munch 1s 1r 2 li ata e Primary Examiner-WE. Ray Assistant Examiner-Stanley J. Witkowski Att0rneyl-lill, Sherman, Meroni, Gross & Simpson ABSTRACT: A monophonic or a polyphonic set of organ pedal key-switches are connected to control electrical signals from tone signal sources, and to direct the tone signals through a filter which passes fundamental bass frequencies, the filter being connected through an amplifier to a speaker. Each key switch is arranged to operate a pedal-cancel circuit for terminating any previously played sustained note that is still sounding. A transistor switch and discharge capacitor are provided which are controlled by the key-switches through the pedal cancel circuit for transferring selected electrical signals to a second filter which passes somewhat higher frequencies, especially the second harmonic, to the same or similar amplifier and speaker. The duration of the signals passing through the second filter is short and is thus electrically or acoustically superimposed on the fundamental signal, thereby simulating the percussive sound of a guitar, especially a bass guitar.

5 01 may 05/ ELECTRONIC ORGAN CIRCUIT FOR SIMULATING GUITAR BACKGROUND This invention relates to a circuit for simulating a guitar sound or effect in an electronic organ, especially a bass guitar effect.

PRIOR ART Heretofore, electronic organs have been equipped with conventional voicing, especially in their pedals, for example, 8- foot and l6-foot voices. Such instruments have been used alone or in combination with others and have previously been unable to provide a guitar or a bass guitar sound unless an additional musician equipped with such an instrument were present to play along with such organ.

SUMMARY OF THE INVENTION According to the present invention, key-switches transfer fundamental frequencies through a filter for reproduction as before. In combination therewith, there are provided means controlled by the key-switches for transferring selected electrical signals to a second filter only during the initial time that each said key-switch is closed. The second filter is constructed to pass somewhat higher frequencies and thus there is electrically or acoustically superimposed on the basic signal a transient signal which is rich in harmonics and which is of short duration, thereby simulating the sound of a plucked guitar string.

Accordingly, it is an object of the present invention to provide an electronic circuit for simulating a guitar sound in an electronic organ.

A further object of the present invention is to provide means for simulating a bass guitar in instruments having monophonic pedal sections and in instruments having polyphonic pedal sections.

A further object of the present invention is to provide means for selectively altering the loudness of a composite signal which is generated from separate components.

Many other advantages, features and additional objects of the present invention will become manifest to those versed in the art upon making reference to the detailed description and to the accompanying sheets of drawings in which preferred structural embodiments incorporating the principles of the present invention are shown by way of illustrative example.

On The Drawings? FIG. I is a schematic diagram of a monophonic circuit for simulating a guitar in an electronic organ;

FIG. 2 is another embodiment of a circuit for simulating a guitar, constructed as part of a polyphonic instrument; and

FIG. 3 is a schematic diagram of a filter circuit used in the embodiments of FIGS. I and 2.

AS SHOWN ON THE DRAWINGS THe principles of this invention are particularly useful when embodied in a circuit for simulating a guitar in an electronic organ such as illustrated in FIG. 1, generally indicated by the numeral 10. The illustrated embodiment is specifically constructed to simulate bass guitar sounds and includes a number of conventional sources of electrical signals having frequencies corresponding to a musical scale, the same being generally indicated at 11. A series of pedal key-switches 12 are arranged to selectively transfer electrical signals from the source of signals 11 to a first filter 13 which is constructed to pass fundamental frequencies, here only bass signals, to an amplifier 14 and speaker 15.

The pedal key switches 12 comprise a series-opening sequence mechanism wherein all of the movable elements of the switches are energized through a resistor R2 by a DC- power supply. This arrangement enables only one pedal note to be played at a time, the lowest of two simultaneously depressed keys taking precedence.

Depressing a pedal actuates one of the key switches 12 to apply potential to a pair of

diodes

16, 17, thereby enabling an electrical tone signal to pass from the corresponding source 11 through the diode 16 and a capacitor C6 into a common pedal collector line 18. The common pedal collector line 18 is connected to a first pedal divider I9 of conventional construction, which reduces the frequency to one-halfof that in the line 18. By this reduction in frequency, namely, by one octave, tone signals are derived for the 8-foot pedal tones in a line 20. The output of the first pedal divider 19 is also connected through a coupling capacitor C9 to a second pedal divider 21, where the frequency of the signal is again divided by two to produce the 16-foot pedal tones that appear in a line or source 22v The

dividers

19 and 21 are conventional countdown dividers that generate square waves as is known in the art. the values of representative components being listed hereafter.

At the same time that the pedal key 12 is depressed, the keying potential is applied to the corresponding diode 17, rendering it conductive and conducting the potential to a pedal keying line 23 which is connected through a diode 24 to the emitter of a PNP type of transistor 25, the base of which is biased to a lesser voltage whereby the transistor 25 emits a signal to a follower transistor 26 to render it highly conductive to apply a potential through the resistors R11 to two pairs of diodes 27-30. The

diodes

27 and 28 couple the l6-foot output signal from the line 22 to the filter l3, and the diodes 29, 30 couple the 8-foot signals from the line 20 to the filter 13.

At the same time that the pedal key 12 is actuated, the keying potential is also applied to the associated sustain capacitor C4 to charge it fully. At the same time that the following transistor 26 applies a potential to the diodes 2730, it also applies to the same potential to a relatively large capacitor C12 to charge it fully, such capacitor being connnected to the input of a further diode 31 which has a relatively high resistance path through the resistor R18 to ground and a relatively low resistance path to ground through a sustain tab switch 32, shown in the on" or open position. When the pedal key 12 is released, the charged sustain capacitor C4 dissipates its charge into the circuit, causing the

diodes

16, 17 to continue to conduct, thereby permitting the tone generator signal to persist. The charge on the capacitor C12 gradually decays and the capacitor C 12 keeps the keying diodes 27-30 conductive so long as it has any remaining charge, after which the remainder of the charge on the capacitor C4 will dissipate to terminate operation of the

dividers

19, 21. If the pedal sustain tab switch 32 is closed, the described sustain function is eliminated. The capacitor C12 is sized to permit the diodes 27-30 to conduct for approximately one second for pedal sustain. This time enables a musician to play one note with his foot, then to move the foot to play a further note with no appreciable silence ensuing during the time that the foot is being moved.

In the event that the musician plays a succeeding note while the preceding note is still sounding, the normally-

inactive dividers

19, 21 would receive conflicting commands, and the resulting effect would be a noisy type of burble or rumble. To prevent such an occurrence, there is provided a pedal-cancel circuit 33 connected to a pedal cancel line 34 which is in this embodiment is the same line as the pedal keying line 23. When one of the pedal key switches 12 is initially closed, keying potential is therefore also applied to the pedal cancel line 34 and conducted through a diode 35 to a pedal cancel transistor 37 connected to a conventional Schmidt trigger circuit or one-shot circuit 36. Thus, when one of the key switches 12 is depressed, the keying potential is present at the collector of the transistor 37. When the pedal key 12 is released, the charge on the capacitor C4 remains. If the next pedal-operated key switch is actuated when one of the capacitors C4 is charged, the base of a transistor 38 of the Schmidt trigger 36 will be rendered less positive by virtue of the action of a resistor R33 connected to the source of keying potential, whereby the transistor 38 will bias the transistor 37 momentarily into conduction, thereby enabling any previously charged capacitor C4 to discharge through the resulting low impedance path to ground, here shown as 8 volts The construction and operation of the Schmidt trigger 36 is conventional, and the duration of the conductivity described through the transistor 37 is extremely short, even though the pedal key 12 is held in a depressed position, whereby the pedal cancel line 34 is in effect grounded for a very short period of time when the playing key 12 is first depressed. During such period of time, the

dividers

19, 21 are kept inactive by the pedal-cancel circuit 33. Following such pulse, the charging of the corresponding capacitor C4 and the capacitor C12 begins. Thus, any.prior-played note is fully canceled before any succeeding note can begin to sound.

A tab switch 39 is provided for the musician to select 8-foot or 16-foot signals, the same being illustrated in the 8-foot position. A set of resistance-shunted tab switches 40, 41 are provided in series with the input to the filter 13, the same being respectively illustrated in the full" volume position. With the switch 4] closed, there is a minimum impedance to the signal, and with it open, the musician has two further choices of level of loudness.

With a bass guitar tab switch 42 in an off positioned (opposite to that illustrated), the circuit thus far described specifically is used to provide conventional pedal tones. in combination therewith, according to the present invention, there are provided means controlled by the key switch 12 for transferring selected pedal signals to a second filter 43 only during the initial time that the key switch 12 is closed.

To this end, the signals on the 8-foot line 20 are divided equally by a pari pair of resistors R9, R between the diodes 29, 30 and a further pair of

diodes

44, 45. When these

diodes

44, 45 are conductive, the 8-foot signal passes through one section 42a of the brass guitar tab switch and hence on through a second set of resistance-shunted

tab switches

47, 48 to the second filter 43. Another section 42b of the bass guitar tab switch 42 is connected in series with the pedals sustain switch 32 so that the sustain-function previously described will always take place when the bass guitar switch 42 is in the on." position. The second set of resistance-shunted

tab switches

47, 48 are respectively mechanically coupled to the switches 40, 41 so that a proper proportion of or magnitude of 8-foot signals are directed to the filters 13, 43. The filter 43 in this embodiment is tuned to cut off and pass frequencies below 600 cycles, being thereby at least sufficiently higher to pass at least the second harmonic of the signals that pass through the filter 13. When the bass guitar tab switch 42 is off" (opposite to that drawn), no signals pass through the filter 43 from the

diodes

44, 45. if desired, the

diodes

44, 45

could obtain tone signals from some other source, such as the l6-foot line 22, or from some other related frequency present in the organ, such as the quint. The arrangement illustrated is preferable largely due to a sense of taste or judgment in the resulting tone.

To control the

bass guitar diodes

44, 45 so that they will be conductive only during the initial time that the key switch 12 is closed, there is provided a bass guitar keyer transistor 49 that is coupled through a capacitor C3 to the pedal cancel line 34 at the collector terminal of the transistor 37. The bass guitar keyer transistor 49 is normally nonconducting its emitter being connected to a power supply, and its base being biased through a resistor R31 to the same potential. When a key switch 12 is actuated, a pulse is produced by the Schmidt trigger 36 which causes a negative pulse to be produced by the canceled transistor 37; the bias applied to the base of the transistor 49 becomes momentarily less than positive and the transistor 49 is rendered momentarily conductive, thereby fully charging a capacitor C1. Such charging produces a DO transient in the second filter 43 before any of said selected electrical tone signals reach said filters 13, 43. The capacitor C3 is quickly fully discharged by such pulse from the pedal cancel transistor 37 before such pulse terminates and controls and limits the effective duration of the time that the transistor 49 is conductive and hence controls the duration of the charging pulse that appears at the capacitor C1 to insure that it is fully charged and to insured that the dissipation of its charge can begin as soon as possible. At the same time that the bass guitar keyer transistor 49 is rendered conductive to cause potential to appear at the capacitor C1, such potential also appears through a resistor Rl on the

diodes

44, 45 to render them conductive. At the same time, a capacitor C2 herein referred to as a second capacitor, is charged through the resistor RI. When the bass guitar keyer transistor 49 goes nonconductive, the capacitor C1 discharges through the resistor Rl in a gradual manner. This discharge time is normally between and 200 milliseconds, while the discharge time for the capacitor C12 is normally in the range between 700 milliseconds and 1,000 seconds. "i he output signal on the 8-foot line 20 is substantially an alternating square wave. The capacitor C2 can be recharged from the capacitor C1 via the resistor R1 at a relatively slow rate during part of the tone-signal cycle, and the capacitor C2 can discharge relatively rapidly through the diode 44 during the other part of the tone-signal cycle, thereby altering the shape of the tone-signal to be that of spaced saw-teeth, the waveform that is characteristic of a string instrument. Thus, the

diodes

44, 45 comprise a readout means that controls the tone signals as a function of the decay of the charge on the capacitor Cl, such charge having been derived from a pulse in the pedal cancel line 34. Thus, the transistor 49 comprises a keying transistor disposed between the power supply and the capacitorC l,'such transistor having a connection to the pedal cancel line or circuit and being of the PNP type with a power supply connected to its emitter and the power supply being connected with via the resistor 31 to the base thereof, such base being connected to the pedal-cancel circuit 33.

Thus, also, the pedal cancel transistor 37 on firing provides a negative pulse to the base ofthe bass guitar keyer PNP transistor 49 causing the transistor 49 to conduct momentarily, transferring the emitter voltage to the collector circuit to key the

diodes

44, 45 to transfer the 8-foot pedal tone signals from the first pedal divider 19 through the bass guitar tab switch section 42a to the filter 43. If one of the pedal keys .12 is depressed and released, a conventional bass tone signal passes through the filter 13. This tone signal will have a rapid onset and a gradual decay having a duration on the order of 700 to L000 milliseconds. Because of the effect of a pair of capacitors C10, C11, this tone signal will have a string quality as explained above for the capacitor C2. in synchronism with the onset of the signal through the filter 13, there will be superimposed thereon through the filter 43, a further signal which is particularly rich in the second harmonic which has a rapid onset that begins at the same time, but which has a rapid decay so that its duration is on the order of 150 to 200 milliseconds, even though the key switch 12 is held depressed. These signals in this embodiment are united electrically (and in the other embodiment herein acoustically) to provide a composite audible tone simulating that of a plucked string of an electric bass guitar.

in FIG. 3 there is illustrated schematically representative portions of a polyphonic instrument showing the invention as it is applied thereto. Here the circuit for simulating string and bass guitar sounds is generally indicated by the numeral 50, wherein a pair of separate amplifiers 51, 52 are used along with separate speakers 53, 54 to combine the basic components of the guitar tone signal acoustically. For convenience, the resistance-shunted tab switches for regulating the volume have been omitted. Only one one representative voicing tab switch 55a is shown in association with isolation resistors R46. When these have a value of 270 K ohms, a flutelike signal is obtained and where such resistance is on the order of 150 K, the voicing is that of tibia. Further, for simplicity, the circuitry involving 4-foot and l6-foot signals has been omitted.

The portion of the circuit 50 illustrated includes a set of pedal-operated key switches 55, each having a movable element engageable with a contact connected to a DC-power supply which is the source of keying potential. The switches 55 are illustrated in their off" position. and when one ofthem is actuated. the keying potential is conducted through a resistor R40 and a normally slightly negatively biased resistor R41. whose bias is thereby overcome, to a pair of keying diodes 56. 57. Only one such pair of diodes is illustrated. they being connected to receive tone signals corresponding to a particular musical frequency. For a full-pedal organ, there would be 25 or 32 such tone-signal sources, the only one illustrated being that one associated with the pedal key C and the corresponding signal source. The representative signal source is thus indicated by the numeral 58. With the keying diodes 56, 57 conductive, the alternating tone-signal is conducted through a resistor R43 which is connected to a pedal collector 59v Similar circuitry connects the other key switches 55 with corresponding sources of electrical signals 58 and appropriate corresponding pedal collectors 59. The pedal collectors 59 are connected through the voicing resistors R46 under the control of the voicing tab switch 55a to a group of four filters 60-63 respectively constructed to pass frequencies below 2l2, l50, 128 and 90 cycles, thus passing the various fundamental frequencies to the amplifier 51.

At the same time that the keying potential appears on the keying diodes 56, 57, such potential also appears on a sustain capacitor C19 to promptly charge the same fully. On release of the key switch 55, the capacitor C19 discharges gradually for between 700 and 1,000 milliseconds, thereby gradually rendering the keying diodes 56, 57 less conductive to the point of nonconduction. As this embodiment is a polyphonic instrument, more than one key switch 55 can be actuated at the same time so that more than one bass tone can be simultaneously produced. When all such pedal keys 55 are released, the corresponding notes that have charged capacitors C19 will be sustained.

This embodiment likewise is provided with a pedal-cancel circuit generally indicated at 64 and including a pedal cancel transistor 65. The pedal cancel transistor 65 has a base that normally is at ground potential because of a resistor R54. However, during the time that the capacitor C19 is being charged, the base of the pedal cancel transistor 65 senses the presence of the charging current and the transistor becomes conductive. In so doing, any voltage on a pedal cancel line 66 is grounded through the pedal cancel transistor 65. Thus, if a pedal key switch S5 is actuated at a time when one of the noncorresponding capacitors C19 has a charge remaining thereon, such remaining charge will appear on the line 66 by passing through the offlcontacts of the pedal key switch 55, through a diode 67 to the line 66, whereby all oftheicapacitors C19 are simultaneously discharged which are associated with nonactuated key-switches. Rather than have all the charging current for the capacitor C 19 being charged pass through the emitter of the transistor 65, there is provided in parallel thereto a capacitor C23. As soon as the capacitor C19 is fully charged, there is no further current flow and the base of the transistor 65 will immediately return to ground potential. A resistor R40 thereby determines the length of the charging time of the capacitor C19, and hence the duration of the pedal cancel pulse. All of the capacitors C19 that have been omitted from the drawing are connected to a point indicated by the numeral 68.

The line 66 is connected through one section 69a of a bass guitar switch 69 to a pedal sustain switch 70 whereby the charge on each capacitor C19 is immediately dissipated to ground when both the guitar bass switch 69 and the pedal sustain switch 70 are in the ofF position (not as illustrated).

With the bass guitar switch 69 in the off position, the portion of the circuit 50 thus far specifically described can be used as a conventional pedal bass circuit for an organ. In combination therewith, there are means provided which are controlled by the key switch 55 for transferring selected pedal signals to a second filter 71 only during the initial time that the key switch 55 is closed.

Each of the pedal collectors 59 is directly connected respectively to a further section 69c-69fof the bass guitar switch 69, and signals obtained therefrom are combined by a group of parallel resistors R47 and are conducted via a coupling capacitor C20 to a preamplifier 72. The signals from the preamplifier 72 are conducted via a coupling capacitor C21 to a second preamplifier 73 which along with a diode 74 serves as a readout means. The diode 74 is connected via a pair of resistors R51 and R53 to the filter 71. The resistor R51 and a resistor R52 have an isolation function, and the resistor R53 along with a capacitor C22 serve to attenuate the higher frequencies that are passed by the filter 71.

In order to control the conduction of tone signals through the readout means 73, 74, there is provided a further section 6911 in the bass guitar switch 69 which is placed in operative connection with a line 75 used in the pedal sustain circuit. A power supply is connected via a resistor R55 and the switch section 69!; to the line 75 so that every time that the pedal cancel transistor is momentarily energized as previously explained, there will be a voltage drop across the resistor R55 of similar time duration. A guitar bass keyer 76 is a PNP type of transistor, the base of which is biased by the same power supply through a resistor R57, the base being connected through a capacitor C18 and a resistor R56 to the line 75. Thus, each time that the pedal cancel transistor 65 is momentarily conductive, the base of the transistor 76 will become less positive and enable a power supply to conduct a charging current to a capacitor C16 which corresponds to the capacitor C1. The capacitor C16 is connected through a resistor R38 which corresponds to the resistor R1 to the readout means 73, 74 and also to a capacitor C17 which corresponds to the capacitor C2. The capacitor C18 corresponds to the capacitor C3.

In this embodiment, when the bass guitar tab switch 69 is placed in the on" position, as drawn, then playing of the pedal keys 55 produces one component of sound through the amplifier S1 and the speaker 53 as is described above. In addition, the energizing of the pedal cancel transistor 65 momentarily for pedal cancel purposes, also gates the transistor 76 to charge the capacitor C16 to render the readout means 73, 74 conductive for a period of time somewhat less than the discharge time of the capacitor C 19 whereby there will be simultaneously released tone signals having a similar derivation but which are altered by the higher frequency filter 71 to produce a second component sound from the speaker 53, the second component being somewhat shorter and rendered in the shape of the spaced saw-teeth by the capacitor C 17 during the decay of the charge on the capacitor C16.

FIG. 3 shows a schematic diagram illustrating the circuitry of the filters used in the embodiments of FIGS. 1 and 2. This circuit is conventional and is included to provide a complete disclosure to the reader.

The various values or sizes of resistors and capacitors referred to in the specification and/or otherwise disclosed on the drawings are presented in the following table of values:

Resistors, in ohms:

R1, K; R2, 470K; R3, 560K; R4, 33K; R5,

1K; R6, 2.2K; R7, 22K; R8, 22K; R9, 1K; R10, 1K; R11, 39K; R12, 700K; R13, 3.3K; R14, 1K; R15, 100; R16, 220K; R17, 18K; R18, 27K; R19, 39K; R20, 100K; R21, 1.5 meg; R22, 830K; R23, 470K; R24, 33K; R25, 39K; R26, 39K; R27, 470K; R28, 220K; R29, 56K; R30, 10K; R31, 100K; R32, 1K; R33, 12K; R34, 10K; R35, 100K; R36, 2.2K; R37, 33K; R38, 180K; R39, 320; R40, 220; R41, 39K; R42, 56K; R43, 22K; R44, 1K; R45, 100; R46, 270K or K; R47, 22K; R43, 560K; R49, 3.9K; R50, 100K; R51, 470K; R52, 33K; R53, 220K; R54, 470; R55, 100K; R56, 10K; R57, 100K; R58, 4.7K; R59, 56K, Fig. 1 use; 150K, Fig. 2 use, at 850-; 47K, Fig. 2 use, other R60, 100K; R61, 100K; R62, 270K; R63, 270K; R64, 150K for Fig. 1; see note for Fig. 2 use; R65, 180K; R66, 33K for 150-, Fig. 1 use; 50K for 600-, Fig. 1 use; see note for Fig. 2 use; R67, 3.3 meg; R68, 270 for Fig. 1 use; 220 for Fig. 2 use; R69, See Note.

NOTE: This value is adjusted, as by selection, to tune the filter to the excel: frequency indicated.

Capacitorsvalues in Mfds:

C1, .47; C2, .033; C3, .22; C4, 5; C6, .0012; O7, .0058; C8, .001; C9, .01; C10, .082; C11, .047; C12, C13, .0047; C14, .33; C15, .01; C16, .27; C17, .022; C18, .22; C19, C20, 10; C21, .22; C22, .01; C23, 70; C24, .02.

Filter Frequency 90- 128- 150- 212- 600- 850- C25. .068 047 .033 .022 .0068 Omit C26- 01 .0068 0047 .0033 0015 001 C27. .01 0068 .0047 0033 0015 001 C28 .022 015 01 0068 0022 .0015 C20 022 015 01 0068 0022 0015 C30, Fig. 1 use .1 02 C30, Fig. 2 use .082 068 047 .033 .082 C3 .01.

Although various modifications might be suggested by those versed in the art, it should be understood that 1 wish to embody within the scope of the patent warranted hereon, all such embodiments as reasonably and properly come within the scope of my contribution to the are.

I claim:

1. A circuit for simulating a guitar in an electronic organ, comprising:

a. a number of sources of electrical signals having frequencies corresponding to a musical scale;

b. amplifier means connected to speaker means;

c. a first filter for passing fundamental frequencies and a second filter for passing somewhat higher frequencies and each connected to the input of said amplifier means;

d. a series of key-switches respectively connected to selectively transfer electrical signals of a selected frequency to said first filter; and

e. means controlled by said key-switches for transferring electrical signals of said selected frequency to said second filter only during the initial time that each said key-switch is closed.

2. A circuit for simulating a guitar according to claim 1,

wherein said transferring means includes:

a. a capacitor subjected to a charge in response to closing of said key switch; and

b. a readout means connected to control the selected electrical signals in response to the decay of said charge on said capacitor.-

3. A circuit for simulating a guitar according to claim 2, including a second capacitor connected to be charged through a resistor by said first-named capacitor and to be more rapidly discharged through said readout means.

4. A circuit for simulating a bass guitar according to claim 2 in which said capacitor is charged by a pulse derived from a pedal-cancel circuit under the control of said key switch.

5. A circuit for simulating a bass guitar according to claim 4 which includes a further capacitor discharged by said pedalcancel circuit for limiting the effective duration of said charging pulse and for assure assuring full charging of said firstnamed capacitor.

6. A circuit for simulating a bass guitar according to claim 4 which includes a keying transistor connected between a power supply and said capacitor, and a connection from said pedalcancel circuit to said transistor through which connection said transistor is controlled to pass said pulse.

7. A circuit for simulating a bass guitar according to claim 6 in which said keying transistor is of the PNP type, the power supply being connected to its emitter and via a resistor to its base, the base having said connection from said pedal-cancel circuit.

8. A circuit for simulating a guitar according to claim 1, including:

a. a first set of resistance-shunted tab switches in series with said first filter; and

b. a second set of resistance-shunted tab switches in series with said second filter, each switch in said second set being mechanically coupled to a corresponding switch in said first set.

9. A circuit for simulating a guitar according to claim 1, including a preamplifier connected to amplify said signals for said second filter.

10. A circuit for simulating a guitar according to claim 2, in which said readout means comprises a preamplifier.

l l. A circuit for simulating a guitar according to claim 4, including:

a. a normally inactive divider forming part of the connection between said sources of electrical signals and said first filter, and being active under the control of said key switches; aa and b. said pedal-cancel circuit being connected to control said divider for controlling said transfer of electrical tone signals to said first filter, said pedal-cancel circuit effecting full charging of said capacitor and hence a DC- transient in said second filter before any of said selected electrical signals reach said filters.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 79 Dated J n ry 1971 Inventor(s) Alberto E. Kniepkamp It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Page 2 C01. 6, l. 61, change "700 K" to --700--;

Col. 6, I. 64, change "830 K" to --820 K--;

Col. 7, 1. 7, correct the spelling of "exact";

C01. 8, 1. 15, delete "assure"; and

C01. 8, l. 45, delete "aa".

Signed and sealed this 11th day of January 1972.

(SEAL) Attest:

EDWARD M.FLETCHER, JR. ROBERT GOITSCHALK Attesting Officer Acting Commissioner 01 Pate

Claims

1. A circuit for simulating a guitar in an electronic organ, comprising: a. a number of sources of electrical signals having frequencies corresponding to a musical scale; b. amplifier means connected to speaker means; c. a first filter for passing fundamental frequencies and a second filter for passing somewhat higher frequencies and each connected to the input of said amplifier means; d. a series of key-switches respectively connected to selectively transfer electrical signals of a selected frequency to said first filter; and e. means controlled by said key-switches for transferring electrical signals of said selected frequency to said second filter only during the initial time that each said key-switch is closed.

2. A circuit for simulating a guitar according to claim 1, wherein said transferring means includes: a. a capacitor subjected to a charge in response to closing of said key switch; and b. a readout means connected to control the selected electrical signals in response to the decay of said charge on said capacitor.

5. A circuit for simulating a bass guitar according to claim 4 which includes a further capacitor discharged by said pedal-cancel circuit for limiting the effective duration of said charging pulse and for assure assuring full charging of said first-named capacitor.

6. A circuit for simulating a bass guitar according to claim 4 which includes a keying transistor connected between a power supply and said capacitor, and a connection from said pedal-cancel circuit to said transistor through which connection said transistor is controlled to pass said pulse.

8. A circuit for simulating a guitar according to claim 1, including: a. a first set of resistance-shunted tab switches in series with said first filter; and b. a second set of resistance-shunted tab switches in series with said second filter, each switch in said second set being mechanically coupled to a corresponding switch in said first set.

11. A circuit for simulating a guitar according to claim 4, including: a. a normally inactive divider forming part of the connection between said sources of electrical signals and said first filter, and being active under the control of said key switches; aa and b. said pedal-cancel circuit being connected to control said divider for controlling said transfer of electrical tone signals to said first filter, said pedal-cancel circuit effecting full charging of said capacitor and hence a DC-transient in said second filter before any of said selected electrical signals reach said filters.