US3746775A - Keyer circuit for electronic musical instrument - Google Patents

Keyer circuit for electronic musical instrument Download PDF

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Publication number
US3746775A
US3746775A US00235350A US3746775DA US3746775A US 3746775 A US3746775 A US 3746775A US 00235350 A US00235350 A US 00235350A US 3746775D A US3746775D A US 3746775DA US 3746775 A US3746775 A US 3746775A
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Prior art keywords
fet
circuit
keyer
gate
capacitor
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US00235350A
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English (en)
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Y Uchiyama
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Nippon Gakki Co Ltd
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Nippon Gakki Co Ltd
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    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10H—ELECTROPHONIC MUSICAL INSTRUMENTS; INSTRUMENTS IN WHICH THE TONES ARE GENERATED BY ELECTROMECHANICAL MEANS OR ELECTRONIC GENERATORS, OR IN WHICH THE TONES ARE SYNTHESISED FROM A DATA STORE
    • G10H1/00—Details of electrophonic musical instruments
    • G10H1/02—Means for controlling the tone frequencies, e.g. attack or decay; Means for producing special musical effects, e.g. vibratos or glissandos
    • G10H1/04—Means for controlling the tone frequencies, e.g. attack or decay; Means for producing special musical effects, e.g. vibratos or glissandos by additional modulation
    • G10H1/053—Means for controlling the tone frequencies, e.g. attack or decay; Means for producing special musical effects, e.g. vibratos or glissandos by additional modulation during execution only
    • G10H1/057—Means for controlling the tone frequencies, e.g. attack or decay; Means for producing special musical effects, e.g. vibratos or glissandos by additional modulation during execution only by envelope-forming circuits
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S84/00—Music
    • Y10S84/23—Electronic gates for tones

Definitions

  • a sustain keyer circuit comprises a field effect transistor, a resistor and a key-operated switch all connected in series between a ground a power line.
  • An input tone signal supplied to the gate of the FET is keyed to appear at the drain thereof.
  • a capacitor is connected across the keyoperated switch. Between the capacitor and the ground is connected another FET which is switched on and off by a rectangular wave having a supra-audible frequency and a variable duty factor thereby exhibiting a variable average resistance, determining a sustain time in cooperation with the capacitor.
  • FIG. 20 I PRIOR ART I I"- I I I i A I 0.1 l FIG. 2d TIME".
  • FIG. 5 LB TRIANGULAR SCHMITT WAVE GEN TRIGGER KEYER CIRCUIT FOR ELECTRONIC MUSICAL INSTRUMENT BACKGROUND OF THE INVENTION 1.
  • the present invention is concerned with a sustain keyer circuit for use in an electronic musical instruvoltages of the FETs employed.
  • FIG. 1 which comprises first and second FETs Q and Q, which are connected in series to each other from both DC and AC viewpointsL
  • the first FET Q has its source electrode grounded, with the gate electrode being adapted to receive 'a tone signal through an input terminal T while thedrain electrode isconnected to the source-electrode of the second FET 0,.
  • This second FET Q is connected, on the one hand, to a voltage source Vd via a loadresistance element R and, on the other hand, to an output terminal T through a capacitor C, thus forming an electronic switch which functions as a keyernFor thesake of keying, a series circuit consisting of a resistance element R, and akey-operated switch S, is provided'between the voltage source Vd and thegateof thesecondFET O to thereby switch a keying voltage to be applied to the gate electrode ofv the second-FET O by the operation of the key-operated switch 8,.
  • the above-mentioned series circuit further includes a capacitor C,.connected in parallel therewith, that is, between the.
  • a keying circuit having a time constant determining function, so that the above-mentioned tone signal applied to the FET Q, may be derived at the output terminal T upon keying of the key-operated switch 8,.
  • a third FET Q is connected to the gate electrode of said second FET Q, at its drain electrode which serves as a sustain time control circuit.
  • the source electrode of the FET O is grounded and the gate electrode thereof is connected to a slidably movable'contact r, of a variable resistor R, such as a potentiometer which is interposed between the'ground and a variable DC potential source, i.e., the
  • the above-mentioned sustain keyer circuit and the FET Q, constituting a sustain time control circuit are By the operation of the variable resistor R, the sustain time, namely, the decay time of tone output signals at the whole keyer circuits after the keying-off of the corresponding number of key-operated switches S, may be adjusted simultaneously to the desired period of time by way of the FETs 0,.
  • each FET Q will increase as, for example, the position of the slidable contact r, of the variable resistor R, is brought closer to the ground side thereof, and that, therefore, the transient time of charging of the capacitor C,, namely, the sustain time in the electronic musical instrument, will vary in accordance with the potential at the gate of each FET O in other words, in accordance with the position of the slidable contact r, of the resistor R,.
  • the resistances of resistors R, and R, and the DC potential of the power source Vd are set so that the FETs Q and Q, are simultaneously rendered conductive ornon-conductive, namely, on or cut-off in accordance with the opened or closed state of the switch 8,.
  • the transient characteristic (response) in the course of the beginning of conduction of the FET Q, and the FET Q is determined by the time constant which, in turn, is determined by the capacitance of the capacitor C, and the resistance of the resistorR, to thereby determine the build-up characteristic of the tone signal derived from the output terminal T while whenever the key-operated switch S, is opened, the transient characteristic (response) in the course of the ending of conduction of both the FET Q, and the FET Q, is determined by the time constant which, in turn, is determined by both of the value of capacitance of the capacitor C, and the value of resistance produced between the drain electrode and the source electrode of the FET Q; to thereby obtain the desired decay characteristic of the thus developed tone output signal, which can be termed sustain time.
  • FIG. 2 a shows the gate-source voltage Vgs to drainsource current I characteristic of a P channel enhancement mode MOS type FET as the FET Q, where Vth represents the gate cutoff voltage thereof. Accordingly, when a gate voltage Vg as shown in FIG.
  • another FET determining the sustain time constant following the opening of a key-operated switch together with a capacitor in a time constant circuit in the sustain keyer and having its gate to vary its equivalent resistance value in accordance with a rectangular waveform signal applied thereto, which signal has a variable duty factor controllable by an instrument player, thereby controlling the sustain characteristic uniformly, independently of the inconsistency in the gate cutoff voltages of the FETs employed.
  • a further object of the present invention is to provide sustain keyer circuits for use in an electronic musical instrument, which are capableof reducing signal leakage occurring upon mixing a plurality of keyed tone signals.
  • a still further object of the present invention is to provide sustain keyer circuits for use in electronic musical instruments, which are caused to reduce signal leakage due to the capacitance between the gate electrode and the drain electrode of an FET which is employed as the keyer.
  • FIG. 1 is a circuit diagram illustrating a prior art keyer circuit for use in an electronic musical instrument, said keyer circuit employing FETs therein.
  • FIG. 2 a through d are charts for explaining the operation of the prior art keyer circuit, wherein FIG. 2 a is a characteristic curve of the gate-source voltage Vgs to the drain-source current I in an enhancement mode F ET; FIG. 2 b is the waveform of a voltage which is applied to the gate G of FET 0,, shown in FIG. 1; FIG. 2 c is a waveform showing an output signal at the circuit of FIG. I; and FIG. 2 d is a waveform showing an output signal at the circuit of FIG. 1 in decibels.
  • FIG. 3 is a circuit diagram of a sustain keyer circuit illustrating an embodiment of the present invention.
  • FIG. 4 is a diagram showing a waveform of an output tone signal derived from the sustain keyer circuit of FIG. 3.
  • FIG. 5 is a circuit diagram representing a modification of a part of the circuit shown in FIG. 3.
  • FIGS. 6 and 7 are circuit diagrams showing other em bodiments of the present invention, respectively.
  • a keyer circuit arrangement which comprises: a p-type enhancement mode FET Q with grounded source electrodes S, whose gate electrode G is adapted to receive a tone signal through the input terminal T, from a known tone generator such as a flip-flop circuit not shown and whose drain electrode D is connected directly to a mixing load resistor R as well as to the output terminal T which is common to a plurality of keyer circuits dealing with respectively different tone signals; a series circuit of a key-operated switch 8,, a resistor R and a first resistor 1 connected between the drain electrode of FET Q11 and a power source line --Vd to form a keying circuit, va second resistor R connected in parallel with the FET Q between the drain and source electrodes thereof, a capacitor C connected between the juncture of the resistor R and the resistor R and the power line (as an A.C.
  • a p-type enhancement mode FET Q as a switching element with its drain electrode connected at the connection point between the capacitor Cd and the resistor R and its source electrode grounded.
  • the FET Q22 has its gate electrode adapted to receive a rectangular wave signal from a rectangular wave generator A to be rendered alternately conductive and non-conductive.
  • V represents the voltage across the capacitor Cd.
  • the capacitor Cd begins charging again through the effective (average) resistance of the FET Q, and the output signal decays gradually thereby.
  • the decaying characteristic of the output signal is determined by a time constant, which is determined by the capacitance of the capacitorCd and mainly the effective drain-source resistance of the FET Q11 (also by the resistance value of the circuit includingthe resistor R the resistor R, and the FET Q Accordingly, the decaying characteristic of the tone signal after keying-off, namely the so-called sustain characteristic, can be varied by varying the effective drain-source resistance of the FET 0,, as required.
  • FIG. 5 there is shown an example circuit for controlling the FET Q", in which arrangement is provided so that the output signal produced in a triangular waveform having a predetermined repetition frequency, such as 40 kHz, which is higher than the audible frequency and which is obtained from a triangular waveform generator G is applied via a DC blocking catain keys circiiit and the aforesaid FET Q22 are propacitor C and a diode D in this order, to the input side of the known Schmitt trigger circuit F which is comprised of elements such as transistors and resistors, and
  • the aforesaid circuit arrangement is operative in such a way that, by changing the DC potential of the point 'Hbr" connection between the capacitor C and the diode D via a variable resistor R which is interposed vided in, for example, the console of an electronic musical instrument each in number corresponding to the multiplicit number of tone generators installed in accordance with the number of the keys of the electronic musical instrument.
  • such elements as the triangular waveform generator G, the variable resistor R B and the Schmitt trigger circuit F are provided one each in such a waytha'ma combination of these elements is used in common'to said multiplicit number of FET Q to continuously effect simultaneosus change of the conductive time of said multiplicity of FET On by changing the duty factor of the rectangular waveform signal generated at one output terminal T, of said Schmitt trigger circuit F.
  • the circuitry is in the state such that the DC level of an output signal form the triangular wave generator G is set at a predetermined value by means of the variable resistor R and that the duty factor of the rectangular wave produced at the output of the Schmitt trigger circuit F is set at a predetermined value to have the conducting to nonconducting time ratio of the FET Q set at a predetermined value of the order of, for example, 0.5
  • the keyoperated switch S is opened in such a state of the circuitry, the drain electrode of the FET Q1 and the drain electrode of the FET Q are at the ground potential. So, this latter FET Q is held in its cut-off state.
  • the tone signal which is always applied to the gate electrode of the FET Q does not appear at the drain side of the FET Q .
  • the capacitor C which is connected through resistor R to the drain electrode of the FET Q is in the state of being charged up with the voltage of the power source V,, by the repetition of the momentary conducting which is effected between the drain electrode and the source electrode of the FET O with the junction between the capacitor C, and the FET 0,, being at a voltage potential substantially equal to the ground potentialzero.
  • the FET Q will become conductive as the tone .signal which is applied to the input of the FET Q11 is derived, as the output tone signal having a build-up characteristic in accordance with the characteristic of the keyer circuit, at the output terminal T, via the drain electrode of this FET Q
  • the tone signal thus derived may be amplified as desired to be converted to an audible sound wave to be given out from such an appliance 'as a loud speaker not shown.
  • the capacitor C which has been in the state of i being discharged in the mode of operation described above begins to be charged up with the voltage of the power source -V through the average (effective) resistance between the source and the drain of the FET O which is rapidly switched to be momentarily conducting and momentarily non-conducting, and along with this, the drain potential of the FET Q11 as well as the drain potential of the FET Q22 approach the ground potential.
  • the FET Q will produce no output at its drain electrode in the same manner as that described in connection with the opened state of the key-operated switch 8,.
  • the decaying characteristic of the output signal is determined by the time constant which is determined by the combination of the capacity of the capacitor C the average resistance resulting from the conducting to non-conducting time ratio between the drain and the source electrodes of the FET Q22, and a series resistance of resistors R and R (also incluing the FET Q).
  • the aforesaid sustain time or the decay time of an electronic musical instrument may be controlled by varying the DC level of the triangular waveform signal applied to the input side ofthe Schmitt trigger circuit F, by altering the resistance value of such an element as the variable resistor R B to thereby alter the duty factor of the rectangular waveform output signal derived at the output of said Schmitt trigger circuit F, whereby continuously varying both the momentary duration of cut-off time and the momentary duration of conducting time of the FET Q For example, from a viewpoint of the duty factor, when the momentary conducting period of time is considerably smaller as compared with the momentary cut-off period of time, the length of charge-up time of the capacitor C
  • the sustain time or the decay time of the tone signal which is derived at the outputterminal T, under the aforesaid condition will be prolonged.
  • the momentary conducting period of time of the FET Q is substantially great as compared with its momentary cut-off period of time, the length of charge-up time of the capacitor C, following the opening of the key-operated switch S is reduced, so that the sustain time or the decay time of the aforesaid tone signal will become shorter. In this way, the sustain time of an electronic musical instrument can be controlled.
  • the circuitry is arranged in such a way that the gate potential of the FET Q is controlled at a very high repetition rate, such as 40 kHz so that this FET 0,, can alternately become fully conductive and fully nonconductive.
  • the FET Q22 can effect the switching between its cut-off state and its conductive state at a high speed, regardless of the gate cut-off voltage of this FET Q-
  • the FET O1 is always held in either the fully conducting or fully non-conductive state, and the average (effective) internal resistance between the drain and the source electrodesof this FET 0,, will be caused to vary by the varying duty factor.
  • the voltage to current characteristic is of a value equivalent to that of a variable resistor having a linear voltage to current characteristic.
  • the decay characteristic of the tone signal within the aforesaid sustain time can be obtained as one which is quite close to a complete rectilinear line as shown by the envelope straight lines in logarithmic (dB) scale, so that the optimum auditory exponential decay pattern can be obtained.
  • the circuitry of the present invention is of many advantages that it can be produced easily and at a low cost, which is highly useful industrially.
  • a keyed tone signal may be derived at the junction between the resistor R and the keyer FET Q in each keyer circuit regardless of the inconsistency in the gate cut-off voltages of the FETs which are employed.
  • a resistor R connected to the source electrode of the FET Q33 serves to reduce the inter-modulation distortion in the resulting tone signal which may take place due to the changes in the resistance of the FET Q when looking at from the drain side thereof, which changes are caused by the variations in the drain potential of other keyer circuits.
  • FIG.-7 shows a further embodiment of the present invention which is intended to reduce as much as possible the signal leakage occurring due to the gate-drain capacitance of the keyer FET Q as a rectangular waveform signal is applied to the input of this keyer FET.
  • the signal leakage is considered to be caused because the applied rectangular waveform contains very high harmonics, in other words, because such rectangular wave contains harmonics over the range up to about 1 MHz clearly.
  • the circuit of FIG. 6 is further provided with another FET 0 between the keyer FET Q and the input terminal T in each keyer circuit to become of a circuit as shown in FIG. 7.
  • To the gate electrode of the FET Q11 is connected the drain electrode of the FET Q44 nd a capacitor at'its one end and grounded at the other end.
  • the input terminal T is connected to the source electrode of the FET Q whose gate electrode is connected to the power source V,,.
  • the FET Q which is thus arranged is employed as a resistance element capable of exhibiting a high resistance value, for example, M 0..
  • the capacitor C is set to have the capacitance of 1 pF, for example.
  • a kind of low pass filter which comprises the drain-source resistance of the FET Q and the capacitance of the capacitor C to thereby eliminate higher harmonics of the rectangular waveform input signal beyond the order of, for example, 16 kHz, resulting in an extreme reduction of signal leakage due to the gate-drain capacitance of the keyer FE Q Furthermore, even if a mans finger contacts the input terminal T there arises no danger of causing the breakdown of the FET 0,, caused by an electro statical shock, since a high resistance of the FET Q is interposed between the input terminal T, and the FET Qu.
  • the novel keyer circuit arrangement of the present invention not only provides desired keyer characteristics by overcoming the problem of inconsistency in the gate cut-off voltages of the FETs employed, but also it can prevent a signal leakage which can take place upon the mixing of keyed tone signals of different keyer circuits and can reduce any signal leakage source line; from the gate-drain capacitance of each keyer FET. It is to be noted that the above-mentioned circuit arrangement is very much Suitable for and convenient to circuit integration (IC production).
  • a sustain keyer circuit comprising:
  • a first field effect transistor having a source electrode connected to said ground means, a gate electrode connected to said input terminal and a drain electrode connected to said output terminal;
  • a rectangular wave generator for generating a rectangular wave signal having a frequency above audible range and a duty factor variably controlled by the instrument player, said generator being connected to said switching element for rendering said element alternately conductive and nonconductive in response to said rectangular wave thereby exhibiting an average resistance, which resistance and gate and the capacitance of said capacitor cooperatively determining a decaying time constant of the circuit.
  • a second FET having its gate connected to the drain of said first FET and its drain connected to the output terminal and a load resistor for enabling the mixing of keyed tone signals coming from other keyer circuits respectively of the same construction as said keyer circuit, the drains of the respective second FETs being connected to said output terminal and the load resistor.
  • a third FET is provided between said input terminal and the gate of said first FET for exhibiting a high resistance and a capacitor is connected between the gate and the source of said first transistor, thereby reducing signal leakage of the keyed tone signals due to the gatedrain capacitance of said first FET.
  • said switching element is an FET whose drain is connected to said capacitor, and whose gate is connected to said rectangular wave generator.
  • said rectangular wave generator comprises a triangular wave generating circuit, a Schmitt trigger circuit adapted to receive the output signals of a repetition freuquency coming from said triangular wave generating circuit and also to generate a rectangular wave, and means for varying a DC input potential applied to said Schmitt trigger circuit.
  • said means for varying the DC input potential comprises a variable resistor connected to said Schmitt trigger circuit for varying the DC input potential of the Schmitt trigger circuit.

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Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3924505A (en) * 1973-11-14 1975-12-09 Hammond Corp Electronic keying circuit with selectable sustain characteristics
US4090426A (en) * 1975-06-20 1978-05-23 Norlin Music, Inc. Contour generator for audio signal
US4173916A (en) * 1974-10-18 1979-11-13 Matsushita Electric Industrial Co., Ltd. Tone generator system for an electronic organ
US4205581A (en) * 1976-10-27 1980-06-03 Kimball International, Inc. Keyer system
US4215615A (en) * 1978-03-20 1980-08-05 Itt Industries, Incorporated Monolithic integrated selection circuit
US4229731A (en) * 1978-04-01 1980-10-21 Itt Industries, Inc. Monolithic integrated organ gate circuit
US4236437A (en) * 1979-03-26 1980-12-02 Kimball International, Inc. Organ brass pulse keyer
US4253369A (en) * 1978-06-20 1981-03-03 The Wurlitzer Company Digital control of attack and decay
US4278001A (en) * 1979-12-26 1981-07-14 Marmon Company Selective keyer biasing to enhance percussion effect
US4545279A (en) * 1981-08-13 1985-10-08 Kabushiki Kaisha Suwa Seikosha Electronic music note generator
US5014587A (en) * 1989-10-16 1991-05-14 The Quaker Oats Company Electronic piano tone circuit
US5424488A (en) * 1993-06-07 1995-06-13 Aphex Systems, Ltd. Transient discriminate harmonics generator

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS54859U (ja) * 1977-06-03 1979-01-06

Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3626074A (en) * 1969-06-24 1971-12-07 Nippon Musical Instruments Mfg Touch-responsive tone envelope control circuit for electronic musical instruments
US3626075A (en) * 1969-07-12 1971-12-07 Nippon Musical Instruments Mfg Touch-responsive tone envelope control circuit for electronic musical instruments
US3626078A (en) * 1968-09-03 1971-12-07 Nippon Musical Instruments Mfg Combination of musical effect system and knee control
US3637913A (en) * 1970-07-27 1972-01-25 Columbia Broadcasting Syst Inc Tone generator employing asymmetrical wave generator rectangular
US3644750A (en) * 1970-06-17 1972-02-22 Gen Instr Microelect Two-phase logic circuit
US3651730A (en) * 1969-09-10 1972-03-28 Nippon Musical Instruments Mfg Sound level control device in electronic musical instrument employing touch responsive keying means
US3652774A (en) * 1969-10-16 1972-03-28 Nippon Musical Instruments Mfg Keying system for electronic musical instruments
US3662188A (en) * 1970-09-28 1972-05-09 Ibm Field effect transistor dynamic logic buffer
US3665091A (en) * 1969-04-14 1972-05-23 Nippon Musical Instruments Mfg Control circuit for sustain keyer circuit in electronic musical instrument

Patent Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3626078A (en) * 1968-09-03 1971-12-07 Nippon Musical Instruments Mfg Combination of musical effect system and knee control
US3665091A (en) * 1969-04-14 1972-05-23 Nippon Musical Instruments Mfg Control circuit for sustain keyer circuit in electronic musical instrument
US3626074A (en) * 1969-06-24 1971-12-07 Nippon Musical Instruments Mfg Touch-responsive tone envelope control circuit for electronic musical instruments
US3626075A (en) * 1969-07-12 1971-12-07 Nippon Musical Instruments Mfg Touch-responsive tone envelope control circuit for electronic musical instruments
US3651730A (en) * 1969-09-10 1972-03-28 Nippon Musical Instruments Mfg Sound level control device in electronic musical instrument employing touch responsive keying means
US3652774A (en) * 1969-10-16 1972-03-28 Nippon Musical Instruments Mfg Keying system for electronic musical instruments
US3644750A (en) * 1970-06-17 1972-02-22 Gen Instr Microelect Two-phase logic circuit
US3637913A (en) * 1970-07-27 1972-01-25 Columbia Broadcasting Syst Inc Tone generator employing asymmetrical wave generator rectangular
US3662188A (en) * 1970-09-28 1972-05-09 Ibm Field effect transistor dynamic logic buffer

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3924505A (en) * 1973-11-14 1975-12-09 Hammond Corp Electronic keying circuit with selectable sustain characteristics
US4173916A (en) * 1974-10-18 1979-11-13 Matsushita Electric Industrial Co., Ltd. Tone generator system for an electronic organ
US4090426A (en) * 1975-06-20 1978-05-23 Norlin Music, Inc. Contour generator for audio signal
US4205581A (en) * 1976-10-27 1980-06-03 Kimball International, Inc. Keyer system
US4215615A (en) * 1978-03-20 1980-08-05 Itt Industries, Incorporated Monolithic integrated selection circuit
US4229731A (en) * 1978-04-01 1980-10-21 Itt Industries, Inc. Monolithic integrated organ gate circuit
US4253369A (en) * 1978-06-20 1981-03-03 The Wurlitzer Company Digital control of attack and decay
US4236437A (en) * 1979-03-26 1980-12-02 Kimball International, Inc. Organ brass pulse keyer
US4278001A (en) * 1979-12-26 1981-07-14 Marmon Company Selective keyer biasing to enhance percussion effect
US4545279A (en) * 1981-08-13 1985-10-08 Kabushiki Kaisha Suwa Seikosha Electronic music note generator
US5014587A (en) * 1989-10-16 1991-05-14 The Quaker Oats Company Electronic piano tone circuit
US5424488A (en) * 1993-06-07 1995-06-13 Aphex Systems, Ltd. Transient discriminate harmonics generator

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