Abstract: The bearing has a fixed portion, and a moving portion, and includes a passive magnetic abutment composed of a fixed element secured to said fixed portion, and of a moving element secured to said moving portion. The bearing further including a passive magnetic centering bearing which is coaxial with said passive abutment, and which is composed of a fixed element secured to the fixed portion, and of a moving element secured to the moving portion, the passive abutment externally surrounding the passive centering bearing, the passive abutment having axial stiffness k.sub.ab, radial stiffness k.sub.rb, a mean radius R.sub.mb, and an inside radius R.sub.ib, and said passive centering bearing having axial stiffness k.sub.ac, radial stiffness k.sub.rc, a mean radius R.sub.mc, and an outside radius R.sub.

Abstract: A device to produce sub-harmonic tone signals in response to a tone signal from a transducer having preferably maximum sensitivity in the plane of bowing of a bowed musical instrument by passing selected cycles of the transducer signal through signal gates which are controlled jointly by sub-harmonic control signals at sub-multiples of the fundamental frequency of the transducer signal and by a signal indicative of the detection of a fundamental frequency. Each sub-harmonic tone signal thus produced has a tone color which approximates that of the corresponding bowed musical instrument of the same frequency range and which is independent of the direction of bowing.

Abstract: The present invention is directed to an electronic musical instrument which has a circuit for calculating a harmonic function corresponding to a fundamental wave. The electronic musical instrument is provided with a circuit for generating, as the harmonic function, an in-tune function corresponding to an in-tune harmonic, a circuit for generating a phase function which imparts an arbitrary frequency number log to the in-tune harmonic and a circuit for multiplying the in-tune function and the phase function, whereby a tone close to a natural tone of an acoustic musical instrument can be created at a relatively low cost.

Abstract: A keyboard operated electronic musical instrument is disclosed which has a number of tone generators each of which is assigned to an actuated keyswitch. Musical waveshapes are generated by a computation using a set of harmonic coefficients. Apparatus is described for generating the set of harmonic coefficients in response to a preselected set of increment number values wherein this set is less in number than the number of harmonic coefficients in a set. The generation of harmonic coefficients is accomplished by computing linear slope variations of groups of coefficients.

Abstract: An electronic musical instrument is provided of the type in which a musical tone signal is formed by executing computations according to a mathematical formula such as a frequency modulation formula. Tone formation of each of musical tone signals to be simultaneously formed is assigned to each time-division-multiplexed time channel which is cyclically repeated over cycles of a plurality of time slots. A computation for forming each single musical tone is divided into a plurality of sub-computations, and those sub-computations are executed respectively using a plurality of cycles of time slots of each single time channel. Thus tone formation according to a complex computation formula is realized. Parameters necessary for the computation are generated respectively for each time slot so that any computational formula is adopted as desired by selecting predetermined parameters for each time slot.

Abstract: In the production of a desired musical waveform by combining harmonic components corresponding to respective harmonic orders, the cut-off harmonic order q.sub.c, each harmonic component value is controlled by selecting the level Ha and the slope of the Formant filter characteristic. The cut-off harmonic order q.sub.c, the level Ha and the slope value can each be varied over a predetermined range. These operations can be performed with a simple circuit arrangement involving a small number of memories. Therefore, the present invention greatly contributes to the reduction of the size and the cost of electronic musical instruments.

Abstract: A keyboard operated musical instrument is disclosed in which the musical tones are generated by reading out data values stored in a waveshape memory. The number of stored data points is reduced by storing the data values in segments corresponding to one-half of the number of data points for a period of a waveshape. By using synthesized data having a symmetry about the midpoint the second half of the waveshape is recovered by a forward and backward memory address read of each waveshape segment. After reading each segment a predetermined number of cycles, an abrupt jump is made to the next segment of waveshape data points.

Abstract: A keyboard operated electronic musical instrument is disclosed which has a number of tone generators that are assigned to actuated keyswitches. Musical tones are produced by computing a master data set from an interpolated sequence of harmonic coefficient values. The master data set points are read out sequentially and repetitively from a memory and converted into an audible tone. A plurality of harmonic coefficient memories are used to store preselected sets of harmonic coefficients. In response to a timing clock, the harmonic coefficients from a cyclically chosen pair of harmonic coefficient memories are selected. A tone having a time variant spectra is produced by using a time variant interpolation between the selected pair of harmonic coefficients.

Abstract: A musical tone producing device of a waveform readout type has a reference waveform memory and a difference waveform memory.The reference waveform memory stores a reference waveform which is similar commonly to each of divided waveforms belonging to a plurality of blocks into which a musical tone waveform of a musical tone to be produced is divided.The difference waveform memory stores difference waveforms, each of which is a difference between the reference waveform and each of divided waveforms.The reproduction of the musical tone waveform is accomplished by reading out the reference waveform and the difference waveforms successively and by successively adding the read out reference waveform and the difference waveforms. This musical tone waveform synthesis according to utilization of difference waveforms contributes to the reduction of memory size.

Abstract: In response to the data input from a keyboard, a tone clock generator generates a tone clock signal. The tone clock signal is counted by a waveform step counter. The output of the counter is used for making an access to a waveform memory. The waveform memory stores first and second waveform data of which the periods respectively are divided into a different number of addresses. One of the first and second waveform data read out from the waveform memory by the output of the counter is selected, according to the key-in data.

Abstract: A keyboard operated electronic musical instrument is disclosed which has a number of tone generators that are assigned to actuated keyswitches. Musical tones are produced by computing a master data set which defines the data points for a period of the musical waveshape. The computation uses a preselected set of harmonic coefficients. The time required to complete a master data set computation is reduced by dividing the set of harmonic coefficients into a number of subsets of coefficients. The harmonic coefficients are combined by a combination of a reverse addressing and complementing in a logic that decreases the required number of computation time intervals.

Abstract: A musical waveshape generator is disclosed in which musical tones at mutation pitches corresponding to an actuated keyswitch are generated by selected attenuation of overtones of a square wave signal. A harmonic suppression means is described which is a combination of a low pass filter, a signal subtractor, and a rectangular waveshape generator whose state changes are controlled by a signal level comparator.

Abstract: A keyboard operated musical instrument is disclosed in which a musical tone having an extended range of harmonics is produced by combining two waveshapes. The first waveshape has a spectrum containing only the odd-numbered harmonics and the second waveshape spectrum has all the harmonics and is phase locked to the first waveshape. The second waveshape has a fundamental frequency which is twice the fundamental frequency of the first waveshape.

Abstract: An electronic musical instrument of the type which synthesizes a musical waveshape from a preselected set of harmonic coefficients is disclosed in which the tonal effects of a set of intramanual couplers is produced. The desired tonal effect is obtained by selecting particular subsets of the harmonic coefficients and combining the selected subsets in response to actuated tone switches.

Abstract: An electronic musical instrument which produces a musical sound by controlling harmonics coefficient and using computing means based on the discrete Fourier transfer. For a fundamental wave, a period function indicated by predetermined period data is generated and, for a harmonic wave, a period function of a period having a predetermined relation to the period of the fundamental wave is generated. By the period function thus obtained, a modulating waveshape memory is read out to obtain modulating data, which is multiplied by a harmonic coefficient.

Abstract: The present invention is a differential sampling circuit for improving the signal to noise ratio by eliminating d.c. level distortion in square wave signals used as components for forming a stairstep or bright wave signal in an electronic organ having multiplexed keying. The multiplexed drawbar signals for even footages at both sides of a sampling resistor are demultiplexed, applied to a sample and hold circuit and applied as inputs to a differential amplifier to cancel any fluctuations of the d.c. signal component.

Abstract: Each one of a plurality of harmonic components is multiplied with a first amplitude coefficient to form a plurality of harmonic components corresponding to a musical tone signal having a desired waveform. Each of the harmonic components is varied with time by a first envelope waveform signal in accordance with a second amplitude coefficient corresponding to each harmonic to form a harmonic component of a spectrum varying with time in a desired manner. By using a second envelope waveform signal, amplitudes of respective harmonic components are varied in a predetermined manner and then the harmonic components are synthesized to form a musical tone.

Abstract: In an electronic musical instrument which produces a musical sound through calculating means of a discrete Fourier algorithm by controlling harmonic coefficients, the value of a harmonic number, more than one temporally changing effect function values and a constant value are added together in a predetermined ratio; the added value is divided into a plurality of blocks; the blocks are subjected to data conversion using plural kinds of functions arbitrarily designated corresponding to the respective blocks and outputted in combination; and the outputs are each multiplied by each harmonic coefficient, thereby controlling the harmonic coefficients with time.

Abstract: In an electronic musical instrument which obtains waveshape amplitude values at sampling points by calculation for producing a desired waveshape, there are provided first means for calculating a waveshape varying with time and second means for calculating a waveshape undergoing no variations with time. Normally the waveshape calculation by the first means is repeated but, in the case of a new key depression or a change in the state of a tone select switch, the waveshape calculation by the second means is performed.

Abstract: A waveform synthesizing apparatus is provided for producing a desired synthesized waveform by adding partial waveforms together. In this apparatus, the times within a cycle wherein a fundamental and harmonics of a desired wave to be output are stored in the circuitry. Peak values of each partial waveform are formed at the prestored times and output at frequencies, which correspond to or exceed sampling frequencies required by each partial waveform. These partial outputs are fed to low pass filters. Each filter has a cut-off frequency component corresponding to each of the output frequencies to remove therefrom clock components. Outputs of the low-pass filters are added together to obtain a synthesized waveform.

Abstract: A tone generating system for an organ comprises a first group of tone generators for producing notes of a first chromatic scale and second group of tone generators for producing notes of a second chromatic scale, slightly offset from the first. The tone generators are addressed via a microprocessor in response to keyboard input, wherein the fundamental and a first plurality of selected harmonic components of a given note are generated by respective tone generators of said first group, and the remaining harmonics are provided by generators of the second group. Harmonic amplitude coefficients for particular organ waveforms are stored in random access memory and are subject to change according to stop inputs coupled to the microprocessor.

Abstract: In a musical instrument having a solo and accompaniment keyboard apparatus is provided whereby an accompaniment tone color is selected which adaptively complements selected solo tones. The first zero crossing spacing of the autocorrelation function for the solo tone is used to implement a tone selection logic. An effective zero crossing is computed for combinations of available accompaniment tones. An accompaniment tone combination is selected whose effective zero crossing has a maximum value that does not exceed a complemented value of the zero crossing for the selected solo tone.

Abstract: A method and an apparatus for producing a musical tone of the so-called partial tone synthesizing type are disclosed, in which the sampling frequencies are established with respect to the respective partial tone components to satisfy the sampling theorem, and the highest frequency among the sampling frequencies is used as a reference frequency. Ratios of sampling frequencies of respective partial tone components to the reference frequency are determined. A partial tone component having a ratio of one is calculated with one channel at a period corresponding to the reference frequency whereas a plurality of partial tone components each having a ratio of less than one are combined into a set wherein the sum of the ratios of the combined partial tone components does not exceed one and the plurality of partial tone components are calculated on the time division basis with one channel at periods corresponding to the respective sampling frequencies.

Abstract: An electronic musical instrument sequentially calculates a plurality of partial tone signals which are amplitude-modulated by a plurality of time window signals, on the time division basis, such that these partial tone signals are synthesized to form a musical tone signal. The instrument includes a circuit means for producing a plurality of predetermined time window signals, an another circuit means for producing a plurality of predetermined partial tone signals and modulating means for modulating the partial tone signals with the time window signals on the time division basis. This instrument makes it possible to form a musical tone having a great number of harmonic components with a simple circuit construction.

Abstract: In an electronic musical instrument, where a musical tone signal having a plurality of partial tone components in a predetermined bandwidth is produced by amplitude-modulating a carrier signal according to a time window signal, there is provided a control means which generates a control signal determining orders of partial tone components to be calculated. In accordance with the control signal the frequency of the carrier signal and the time width of the time window signal. This instrument makes it possible to freely select the frequency bandwidth of the calculated partial tone components, thereby producing a musical tone having a variety of tone colors.

Abstract: In a musical instrument having one or more tone generators in which a plurality of data words corresponding to the amplitudes of points defining the waveform of a musical tone are computed and transferred to a digital-to-analog converter to be converted into musical waveshapes, apparatus is provided for generating tones which are imitative of acoustic signals created by singing or humming. A new tone is obtained by singing into a microphone and actuating a switch. The output waveshapes are generated by implementing a Fourier transform algorithm using a set of harmonic coefficients determined by sampling and processing the signal produced by the microphone.

Abstract: A buzz wave comprising n harmonic components having a flat spectrum envelope is generated according to a relatively simple algebraic expression which can be digitally computed by an arithmetic operation. Modifying harmonic components corresponding to the harmonic components to be emphasized or suppressed are also generated. The buzz wave and the modifying components are added or subtracted to form a desired musical tone signal.

Abstract: A digital electronic organ mixture system comprises a pair of digital organs operatively connected in parallel to the same keyboard or keyboards. The keys are grouped into regions of adjacent keys. In one of the parallel organ systems, the frequency numbers ascend along the keyboard corresponding to the notes associated with the keys. In the other parallel organ system, the frequency numbers are weighted by preselected factors, the factor being the same for each keyboard region, and the factor for each successive region along the keyboard being lower than the factor for the immediately preceding region. Activation of a key along the keyboard produces a pitch series comprising a note produced by the unweighted frequency numbers in one organ system and a second note produced by the weighted frequency numbers in the other organ system. The pitch series breaks back at each successive keyboard region in accordance with the weighting factor for that region.

Abstract: An electronic musical instrument forms output signals having at least one frequency component and an amplitude defining envelope. Output signals are formed for selected string simulators on the instrument so that the notes and chords may be formed simulating a stringed musical instrument by combining the output signals. Various parameters of the amplitude envelope of the output signals may be varied at a user's selection.

Abstract: A tone source circuit for electronic musical instruments, in which a unit phase coefficient corresponding to a note code required by a key depression is read out from a phase coefficient memory of a tone generating part for each time division channel; the unit phase coefficient is applied to an accumulator composed of an adder and an accumulated value storage register to obtain an accumulated value for each time division channel. A demultiplexer for taking out higher order bits of the accumulated value and supplying them as a sampled rectangular wave signal to a filter provided corresponding to each key, the filter eliminates a sampling pulse component from the sampled rectangular wave, and a mixing circuit then mixes the output from the filters.

Abstract: Each harmonic of the ten provided is represented by a pair of binary-valued signals; one having the form A .sym. B .sym. C, where A, B and C are octavely related square waves, and the other being a square wave like C. Each pair of signals is coupled to a resistive divider by coupling elements in an additive relation under control of an individual adjustable voltage source. The coupling elements are weighted so as to minimize distortion in the signal resulting from the mixture. The resistive divider preemphasizes the signals representing each harmonic to compensate for a voltage controlled filter in the audio output used to eliminate high order distortion components. In one embodiment a .div.3 counter followed by a binary counter provides the binary-valued signals for harmonics of order 0.5.times.2.sup.n, where n is an integer, and a binary counter driven in parallel with the .div.3 counter provides the binary-valued signals for harmonics of order 1.5.times.2.sup.n.

Abstract: More than one sub-intervals or time-windows are provided in a one-cycle period of a musical tone selected at a keyboard of an electronic musical instrument. Each time-window passes a sine wave having a frequency predetermined for the time-window. The envelope of the spectrum of a time-window is determined by the shape and the width of the time-window, and the envelope of the spectrum of a sine wave passed from the time-window will become the convolution of the spectrum of the time-window and the frequency of the sine wave. The total area of the frequency spectrum included as frequency components of a musical tone can be covered by several time-windows, each having a different length and passing a sine wave of a different frequency. An amplitude control means controls the amplitude of each sine wave independently. The controlled amplitude level determines the spectrum intensity of the frequency region influenced by the corresponding sine wave.

Abstract: A keying system provides selectable decay times for individual frequency components of a tone to be generated by an electronic organ having a top octave generator producing a multiplicity of rectangular wave signals, and a plurality of associated divider circuits. The keying system comprises a keying block having a plurality of keyer sections. Each keyer section has a first keyer channel comprising at least two MOSFET transistors which are connected in series. At least one keying section further comprises a second keyer channel similar to the first keyer channel, a voltage threshold circuit which has a selectable threshold and switching circuitry to select output signals from either the first or second keyer channel of the one keying section. Each channel of the keying block is connected between a supply voltage and a load resistor which is in turn connected to a reference potential.

Abstract: A keying system provides selectable decay times for individual components of a tone to be generated by an electronic organ having a top octave generator producing a multiplicity of rectangular wave signals, and a plurality of associated divider circuits. The keying system comprises a keyer block having a plurality of identical keying sections. Each keying section comprises at least two MOSFET transistors which are connected in series and the series combination is connected between a supply voltage and a load resistor. A multiple position switch is connected to each load resistor to selectively connect the load resistor to one of a plurality of biasing voltage supplies. Rectangular wave signals from the top octave generator and divider circuits are applied to the gate of one of the transistors in each of the identical keying sections of the keyer block.

Abstract: In an electronic musical instrument apparatus is provided for producing a noise-like signal suitable for a variety of musical effect such as the imitation of percussive musical instruments. A noise master data set is created repetitively and independently of tone generation by computing a Fourier algorithm using random values for the Fourier coefficients. The noise master data set is transferred to a noise tone register whose output is sequentially and repetitively read and converted to an analog noise signal. Formant circuitry is used to vary the noise signal's spectrum in a time variant manner and the frequency of an assigned variable frequency clock can be used to vary the spectral bandwidth of the output noise signal.

Abstract: In a musical instrument having one or more tone generators in which a plurality of data words corresponding to the amplitudes of a corresponding number of evenly spaced reference points defining the waveform of an audio signal are transferred sequentially from a note register to a digital-to-analog converter in repetitive cycles at a rate proportional to the pitch of the tone being generated, apparatus is provided for simultaneously creating tones at two different pitches. The reference points are computed using specified wave shape symmetry characteristics such that a single variable frequency oscillator suffices to generate both tone pitches without requiring separate, or time shared, tone generation channels.

Abstract: A method for producing a tone waveform having a desired spectral construction by modulating an input address signal of a selected frequency for a waveform memory. For the modulation of the input address signal, the output of the waveform memory is multiplied by a parameter .beta. of a suitable value and the multiplication product is added to the input address signal. If the input address varies in the manner of, for example, a saw-tooth wave, a desired tone waveform can be produced within a range between a saw-tooth wave and a sinusoidal wave by selecting a suitable value of the parameter .beta.. More specifically, a saw-tooth wave is produced as a tone wave form if a sufficiently large value of .beta. is selected. As .beta. is gradually decreased, the amplitude is decreased from a higher order and the amplitude also disappears from a higher order until the tone waveform becomes a sinusoidal wave when .beta. is zero.

Abstract: In a musical instrument having one or more tone generators in which a plurality of data words corresponding to the amplitudes of a corresponding number of evenly spaced reference points defining the waveform of one cycle of an audio signal are transferred sequentially from a note register to a digital-to-analog converter in repetitive cycles at a rate proportional to the pitch of the tone being generated, apparatus is provided for computing the set of data points in the note register from a set of points defining a quarter cycle of the waveform. The calculation of the quarter cycle of data points is divided into two sets. One set is calculated using the odd-numbered harmonics and the other set is caculated using the even-numbered harmonics. The complete waveform is reconstructed from the two sets during the transfer of data to the note registers.

Abstract: An electronic music synthesizer capable of simulating a wide variety of musical effects, wherein the settings which create the various effects are hard wired on a plurality of selectable circuit boards so that programming of the instrument can be accomplished by the player with minimum effort. The synthesizer encodes a plurality of keys on the keyboard and selects a tone from the tone generator corresponding to the depressed key. This tone is fed through a chain of dividers to create the needed footages, which are then fed to voicing cards that create the different tone sources for the synthesizer. These tone sources are fed into a state variable active filter which modifies the timbre of the tone sources in order to achieve the desired frequency-related effects.

Abstract: An octave conversion system of the fundamental frequency of an audible tone signal produced by electrically picking up mechanical vibration of a musical instrument in which the audible tone signal and an audible modulation signal having a frequency in a preselected relation to the fundamental frequency of the tone signal are applied to a multiplier which is preferably constituted by a voltage-controlled amplifier. When the modulation signal has a frequency half that of the tone signal, the tone signal is one-octave down-converted, while, when the modulation frequency is equal to the tone signal frequency the tone signal is one-octave up-converted. With this frequency conversion system the fundamental wave component of the octave-converted tone signal has the same envelope as that of the original tone signal. This frequency conversion system is advantageous in attaining small size versions of electric musical instruments and extension of inherent compasses of electric musical instruments.

Abstract: An electronic musical instrument having tone signal sources and keyers for the tone signal sources has a time division multiplexer for multiplexing the key-down information in groups such as for the upper manual, lower manual and pedals. The keyers are provided in divider keyer packages with drawbar, or harmonic content, information being synchronously multiplexed with the key-down information to a single set of keyers.

Abstract: In a modular, expandable organ system comprising a plurality of large scale integrated circuit (LSI) chips an LSI chip is provided which produces frequencies corresponding to notes played on an organ keyboard. Outputs of different duty cycles of rectangular waves are provided for best simulating desired sounds. Other outputs are provided in which the notes are in octave groups facilitating filtering thereof. Each group of outputs has different attack and decay characteristics respectively under the control of the organist so that similar or different types of attack and decay may be provided on different outputs.The present LSI chip provides three generators on one chip. The chips are capable of being interconnected such that any multiple of three generators may be provided.

Abstract: In a circuit for simulating the sound produced when a stringed instrument, such as a bass viol, is plucked, square wave signals of different frequencies from a tone generator are combined to produce a synthesized sawtooth waveform which is applied to a low pass filter to remove the extremely high order harmonics, and then applied to an amplifier the gain of which is controlled in accordance with an envelope signal having a fast attack and a relatively slow decay. The resulting amplified signal is applied to an off-center-biased amplifier which alters the harmonic content of the output signal as a function of decay time such that when the signal is acoustically reproduced it closely simulates the sound produced when a bass viol string is plucked.

Abstract: The specification discloses a pneumatic player piano which utilizes an electric motor roll drive. The roll drive is actuated by a mechanical switching arrangement which responds to the system vacuum so as to simulate the operation of a conventional air motor. The pneumatic stack is constructed to permit the pouch board and valve boxes of an entire level to be fabricated in a single molding operation. The valves themselves are formed of silicone rubber - and require neither backing, facing nor position adjustment.

Abstract: An electronic musical instrument of a waveshape memory type comprising: a plurality of waveshape memories for storing waveshapes of different tone color, and means for variably mixing the outputs of the plurality of waveshape memories for generating tone signals of varying tone color. The mixing ratio of the different waveshapes may be varied with the lapse of time or according to the touch of the key operation or to the tone pitch.

Abstract: DC programmable counters with DC switching provide instant retuning of an entire keyboard of a programmable electronic musical instrument to any one of a plurality of different scales.

Abstract: An electronic musical instrument of a type wherein a plurality of systems are provided each system comprising memories storing respective harmonic component waveshapes which are read at the same reading rate and the read out harmonic waveshapes are suitably mixed to obtain a desired musical tone. Each system also comprises a circuit for controlling the envelope of the waveshapes read from the memories. In the first system, the envelope control is made in such a manner that the envelope will rise upon depression of a key, thereafter maintain a constant level as long as the key is kept depressed and decay upon release of the depressed key. In the second system, the envelope is controlled so that the envelope will rise in a short time and immediately decay thereafter. The respective harmonic waveshapes thus controlled in envelope in the respective systems are then suitably selected and mixed together.

Abstract: The embodiment of the invention disclosed herein is directed to an electronic keyboard musical instrument wherein all the audio frequency signal information is derived from an oscillator multi-frequency generator and frequency divider circuits formed by large scale integrated circuits. The divider circuits associated with various keys of the keyboard generate tone signal information for each of the particular notes of the various octaves. The integrated circuit unit has a plurality of frequency input terminals arranged for connection to the multi-frequency generator and a plurality of second input terminals arranged for connection to its associated key switch on the keyboard of the musical instrument. Actuation of the key switch on the keyboard will enable gate circuits to transfer output signal information from the associated divider into the audio-amplifier stages of the electronic musical instrument.

Abstract: A pulse generator especially for an electronic musical instrument in which a "D" type flip-flop is employed with the logic level at the data input thereof being transferred to the output in conformity with the supply to the clock input of a fixed frequency rectangular wave and the supply to the clear input of a rectangular wave having a frequency which is a whole multiple of the fixed frequency. The output at the output terminal of the flip-flop is a pulse having a duty cycle of predetermined length. The pulses at the output terminal are, of course, repetitive and remain at the same duty cycle without variation. By using a plurality of the flip-flops, each having respective inputs to the clock and clear terminals, a desired range of pitches can be generated.

Abstract: An electronic musical instrument capable of producing any desired combination of two tones of mutually different footage. According to the invention, such combination of tones can be produced from only two tone sources without providing tone sources of an equal number to a total number of footage to be coupled. In view of the fact that musical tone waveshape amplitudes of two coupled tones of different footage can be represented by a multiplication term of a sine wave content and a cosine wave content, these two waveshape contents are individually calculated and then combined to form amplitudes of a composite musical tone waveshape.