US3141919A

US3141919A - System for generating rhythm tones

Info

Publication number: US3141919A
Application number: US58226A
Authority: US
Inventors: Mabuchi Shigeaki
Original assignee: NIHON GAKKI SEIZO KK
Current assignee: NIHON GAKKI SEIZO KK
Priority date: 1959-10-23
Filing date: 1960-09-26
Publication date: 1964-07-21
Anticipated expiration: 1981-07-21

Description

y 21, 1964 SHIGEAKI MABUCHI 3,141,919

SYSTEM FOR GENERATING RHYTHM TONES Filed Sept. 26, 1960 2 Sheets-Sheet 1 Output voltage time y 21, 1964 SHIGEAKI MABUCHI 3,141,919

SYSTEM FOR GENERATING RHYTHM TONES 2 Sheets-Sheet 2 Filed Sept. 26, 1960 Figw 8W Fi gwglp United States Patent YSTEM FOR GlENERATlNG RHYTHM TtlNES Shigealri Mahuchi, Hamamatsu-shi, Japan, assignor to JNihon Galtlri Seize Kabushiki Kaisha, Hamamatsu-shi,

spam

Filed Sept. 26, 1969, Ser. No. 58,226 Claims priority, application Japan Oct. 23, 1959 1 Claim. (Ci. 84--1.26)

This invention relates to electrical musical instruments, and more particularly it relates to a new system for creating rhythm tones in a purely electronic manner.

One conceivable method of electrically creating sounds resembling the sounds of such rhythm instruments as cymbals, triangles, and drums is the conventional method of using a thyratron or other noise generating devices as a noise generating source and utilizing the noise amplified therefrom. The noise obtained from such a noise source is passed through a suitable filter circuit to shape a wave form having the required frequency spectrum.

A system relying on such a method, however, entails the following disadvantages. In the first place, it is ditficult to obtain the desired frequency spectrum by means of a simple filter circuit except in special cases. Accordingly, the tone colors with unique qualities, obtained therefrom become extremely restricted in number. Conversely, if tone colors with ample unique qualities are to be created in great number, the filter circuit will tend to become complex. In the second place, the sounds generated from rhythm instruments are so-called percussive sounds. Such sounds have a wave form wherein the sound wave rises abruptly at the instant of percussion, and its attenuation is exponential. In many cases, the numher of noise like components is large during the rise period while at its peak. During the attenuation, the vibration at the natural frequency, which is determined by such factors as the configuration and material of the musical instruments, becomes intense, and almost all of the noise like components, disappear. For this reason, if a wave obtainable from a noise source is processed with the aim of producing a tone approximating that of a musical instrument, a sound sensation of discord will be produced during attenuation.

The details of the invention will be more clearly apparent by reference to the following detailed description of the invention when taken in connection with the accompanying drawings, in which the same or equivalent parts are designated by the same reference numeral or letters, and in which:

FIG. 1 is a schematic, block diagram showing one example of the invention.

FIGS. 2, 4, 5, and 7 are graphical representations of the output voltage wave forms of the various circuit elements of the embodiment of FIG. 1.

FIGS. 3, 6, 8, 9, and 10 are electrical circuit diagrams showing circuit elements for embodying the system of the invention.

In FIGURE 1 is shown a driving circuit 1; a resonance circuit 2 which produces vibrations when it is driven by the driving circut 1; an amplifier 3 which amplifies the signal voltage obtained through said circuits; a loudspeaker 4 for converting the amplified electric output into sound output; and a contact mechanism 5 for keying the driving circuit 1. The contact mechanism 5 is adapted to be normally controlled by the keys of a keyboard.

FIG. 2 shows a graph ot'output voltage versus time, representing the voltage wave form obtained from the driving circuit 1 of FIG. 1. The particular condition shown is that for the time period when the contact mechanism 5 has been closed. As shown in FIG. 2, this wave form consists of an abrupt rise in output voltage at the ice time of closing the contact and a decrease in output voltage thereafter. This wave form is herein called the driving wave. When the driving wave is impressed on circuit 2, there is produced oscillation at the frequency determined by the parameters of the circuit components. This oscillation is damped by the envelope effect of the driving wave. The manner in which this attenuation occurs is in fluenced principally by the quality factor Q of the resonance circuit and not to a great degree by the character of the attenuation of the driving voltage.

The voltage wave form obtained in the above manner is amplified to the necessary magnitude by the amplifier 3 and is converted into sound output by the loudspeaker 4. By presetting the resonance frequency of the resonance circuit 2 to the frequency which best expresses th musical sensation created by the musical instrument to be represented, the object of the invention is attained.

For the practical realization of the driving circuit 1 in an extremely simple manner, a charging and discharging circuit composed essentially of only capacitors and resistors is sufiicient as is indicated by one example shown in FIG. 3. The driving circuit 1 is connected to a contact mechanism 5 and comprises: a capacitor for charging and discharging 6; a resistor for charging 7; a resistor for discharging 8; a coupling capacitor 9; a direct-current power source 11 supplying a potential of V volts; a junction point A connecting the capacitor 6, resistors 7 and i5, and capacitor 9; an output terminal B; and a ground terminal E, the elements being wire as indicated in FIG. 3. The contact mechanism 5 contains a switch device 10, which is normally open. When said switch device 10 is closed, the electric charge which has been charged in the capacitor 6 is discharged through the resistor 8. Since the resistance of the resistor 8 is substantially lower than the resistance of the resistor 7, the voltage at the point A suddenly approaches the ground voltage. If the switch device 10 is then opened, the recharging of the capacitor 6 will begin through the resistor 7, and the voltage at the point A will assume a value close to the value resulting from the division of the power source voltage V volts by the resistors 7 and 8. The voltage wave form at the point A will be as indicated in FIG. 4, wherein i is the time at which the switch device 10 is closed, and t is the time at which it is opened. This voltage is connected through the capacitor 9 to an outside circuit and, at the same time, it is ditferentiated by the resistance connected between the terminals B and E and the said capacitor 9. As a result, the voltage wave form which appears at the output terminal B is as indicated in FIG. 5.

An embodiment of a driving circuit wherein a transistor is used is shown schematically in FIG. 6. The said circuit is connected to a contact mechanism 5 containing a switch device 26 and comprises, in part: a capacitor 16 for charging and discharging 16; a resistor 17 for charging; a resistor 18 for discharging; a coupling capacitor 19; a direct-current power source 21 (of V volts); and an output terminal B, said elements accomplishing the same functions as their equivalent elements shown in FIG. 3. In addition, the driving circuit 1 shown in FIG. 6 comprises a transistor 12 which has three electrodes, namely, an emitter electrode 13, a base electrode 14, and a collector electrode 15;

resistors

22, 23, and 24; and an input terminal C. The above-stated elements are connected as schematically indicated in FIG. 6. The transistor 12 has the functions of correcting the charging and discharging characteristics of the capacitor 16 and, simultaneously, transmitting the said charged or discharged voltage to the collector electrode 15 through the capacitor 19, which is coupled to the collector electrode 15. The

resistors

22 and 23 are for the purpose of imparting suitable bias voltage to the base electrode 14 of the transistor 12; and, by varying their resistance values, it is possible to vary the point at which the transistor 12 is changed from a conductive state to a cut-off state. The resistor 24 is the load resistance of the transistor 1.2 and is also one of the factors which determine the configuration of the attenuation curve of the voltage wave form illustrated in FIG. 4. The input terminal C is used when input from the outside is necessary.

Transistor 12; is normally in the cut-ofi state. When the switch device 20 is closed, as the voltage of the emitter electrode 13 almost reaches the ground voltage, the transistor becomes conductive. At this time, the voltage of the collector electrode 15 suddenly changes from V volts to the ground voltage. If the switch device is opened, the charging of the capacitor 16 through the transistor 12 and through the

load resistors

24 and 17 begins; the voltage of the emitter electrode 13 gradually approaches V volts; and the transistor 12 is changed little by little into the cut-off state. The wave form of the changing voltage of the collector during this operation assumes the same configuration as that shown in FIG. 4, and a wave form as indicated in FIG. 5 is observable at the output terminal B.

If an input, for example, a white noise voltage, is introduced through the input terminal C, the resulting wave form appearing at the output terminal B will be a superposition of this input wave form on the wave form shown in FIG. 4. The said resultant wave form is indicated in FIG. 7. In this case, the tone color obtainable will be of a diiferent kind.

One example of a simple embodiment of the resonance circuit 2 of FIG. 1 is shown in FIG. 8, wherein the said circuit comprises

coupling resistors

25 and 26; a capacitor 27; and a coil 28. The capacitor 27 and the coil 28 determine the resonance frequency. Upon arrival of an input from the driving circuit 1 of FIG. 1, a vibration at the said resonance frequency occurs; then as the input signal fades out, this vibration is attenuated exponentially. However, the attenuation time differs depending on the magnitude of the quality factor Q of the resonance circuit. That is, resonance circuits with larger Q have longer attenuation times.

The increase of Q of the resonance circuit 2 to the extent of lengthening the vibration attenuating time to several hundred milliseconds by means of a circuit as illustrated in FIG. 8 is normally not simple, because the demand upon the capacitor 27 and the coil 28 becomes severe. For cases wherein such long attenuation times are not required, satisfactory results are obtainable by means of the circuit in the state shown, but when it is desired particularly to lengthen the vibration attenuating time, a circuit as represented by the embodiment shown in FIG. 9 can be used.

This embodiment has the arrangement of a kind of amplifier and comprises: resistors for

bias

29 and 30; a transistor 31; a load resistor 32; an emitter resistor 33 for the said transistor; and a by-pass capacitor 34. The negative feedback circuit is composed of a direct-current blocking capacitor 35; a frequency eliminating circuit 36, which imparts a sufliciently large attenuation with respect to only a certain frequency; and a coupling resistor 37. In actual practice, a suitable circuit such as, for example, a parallel T circuit or a bridged T circuit, may be used for the frequency eliminating circuit. The circuit of FIG. 9 has, furthermore, a direct-current power source 38 (voltage V volts), an output terminal B, and an input terminal C. Although this circuit has the form of a selective amplifier, the circuit constant is so predetermined that, when an input arrives, oscillation at the frequency determined by the frequency eliminating circuit 36 occurs.

One method for causing this to occur is to provide a parallel T-circuit shown in FIGURE 10 having

resistors

39, 40, 41 and

capacitors

42, 43, 44. If the resistance value of the resistor 41 is sufficiently small in comparison with the values of

resistors

39 and 40, the circuit can be placed in the desired condition. Also, the value of this resistance 41 causes the equivalent Q of the entire circuit 4 of FIG. 9 to vary. Actually, by varying resistance 41, it is possible to cause the damping time of the oscillation to vary.

In comparison with the circuit of FIG. 8, the circuit of FIG. 9 has an output voltage which, at times, is of a magnitude such that it requires almost no amplification. In such cases, it has a functional capacity which includes that of the resonance circuit 2 of FIG. 1 and a part, or all, of that of the amplifier 3.

The object of creating rhythm tones may be achieved by connecting the above-described circuits as indicated in FIG. 1, applying the necessary amount of amplification, and causing the loudspeaker to produce the tones.

The tone colors thus obtained as a result may be thought of as being due to the substitution of the mechanical constructions of actual drums and other percussive musical instruments by equivalent, electrical circuits. By this system, percussive tone effects can be amply expressed. Moreover, the elements of the circuits are extremely simple, and not a single factor causing instability in operation nor a single point of difficulty in design is entailed. Especially, if the embodiments of FIG. 3 and FIG. 8 are combined, not a single active element is contained therein; the number of parts is small; and, moreover, the output voltage obtained is not one which requires much contribution from the amplifier to be connected thereafter. Accordingly, the system can be constructed at extremely low cost.

As was mentioned initially, the tone colors generated by rhythm musical instruments contain many noise factors during the rise period, and the vibratory tones due to natural frequencies become strong during the attenuation period. If this effect is to be realized, the following measure, by way of example, may be taken. The circuits of FIG. 6 and FIG. 9 are combined; a white noise voltage is introduced through the input terminal C of the circuit of FIG. 6; the time constant of the circuit consisting of the capacitor 16 and the resistor 17 is diminished to hasten the attenuation of the output voltage of the white noise; and the resistor 41 of the circuit of FIG. 10 is so adjused and set that, in the circuit of FIG. 9, the attenuation time can be long. If the above described measure is taken, a large amount of white noises will be contained during rising of the sound output and during production of peak output, and only the sound determined by the frequency of the circuit of FIG. 9 will remain during the attenuation process.

In comparison with the case wherein, rhythm tones are created by means of only noises, the use of the present system can produce tone colors which are more agreeable to the ear.

While only one resonance frequency was considered in the above described embodiment, it is possible to in crease the number of resonance circuits such as the circuit 2 shown in FIG. 1; if necessary, thereby generating tone colors with further special qualities. For the realization of such a measure, it is possible, for example, to provide circuits having 11 resonance frequencies by inserting in parallel n circuits each of which is as shown in FIG. 8.

While particular embodiments of the present invention have been described, it will, of course, be understood that the invention is not intended to be limited thereto, since many modifications can be made in the above described details without departing from the nature and spirit of the invention, and it is contemplated by the appended claim to cover all such modifications as fall within the true spirit and scope of the invention.

What I claim is:

In an electrical musical instrument, an arrangement for generating percussive sounds in a loudspeaker having a wave form wherein the sound rises abruptly at the instant of percussion and is exponentially attenuated, the vibrations at the natural frequency being intensified during attenuation, the noise-like components of the sound 5 6 almost disappearing, said arrangement comprising in comsource; a second transistor including an emitter bination; joined to said fifth lead line across an eighth bias rea first stage driving circuit and switch including a DC. sistor, a collector joined to said sixth lead line across power source and first and second lead lines therea ninth load resistor; a by-pass capacitor in parallel from; a PNP transistor including an emitter joined 5 with said eighth bias resistor; a D.-C. blocking capacto said first lead line at a first junction point, a itor in series with frequency elimination means concollector joined to said second lead line at a second nected between said collector and said fifth lead junction point, a base with a base input line; a chargline; a base to said second transistor connected in ing and discharging capacitor in series between said series to said sixth and seventh coupling resistors first junction point and said emitter; a third junc- 10 of said second stage, tenth and eleventh bias resistors tion point between said capacitor and said emitter, between said base and said fifth and sixth lead lines; a third lead line from said third junction point to a twelfth bias resistor between said base and said said first lead line, a first resistor for charging and frequency elimination means, and, an output line a switch in series in said third lead line; a second to the loudspeaker connected to the junction of said resistor acting as a collector load between said sec- 5 collector and said D.-C. blocking capacitor. 0nd junction point and said collector; a third resistor acting as a discharge resistor between said second References Cited in the file Of this Damnt and third junction points, the value of said first re- UNITED STATES PATENTS sistor for charging being substantially higher than said third resistor; fourth and fifth resistors acting 20 g "a f 3 as bias resistors between said first and second lines 2139O23 5 1938 respectively to said base input line; a fourth junc- 2342338 g 1944 tion point between said second resistor and said 2482548 g f 1949 collector a four lead line from said fourth junction O 1949 point acting as the output lead and a coupling capac- 5 2584386 Z? ge 1952 istor in said output lead; 2694954 K i e 1954 a second stage resonance circuit including a coupling 2927282 E 1960 line to said coupling capacitor sixth and seventh 2964654 1960 coupling resistors in series, connected to said coupling 3050642 R Ia am 1962 line, and a capacitor and coil in parallel, between 30 ogers et a said sixth and seventh resistors and, a third stage OTHER REFERENCES amplifying circuit including a second D.-C. source, VEB (German application) 1023957 Feb 6, 1958 fifth and sixth lead lines from said second D.-C.