Abstract: Filter coefficients corresponding to a plurality of discrete cutoff frequencies are stored in advance in a memory and a filter coefficient corresponding to a specified cutoff frequency is generated by performing an interpolation referring to the filter coefficients stored in the memory, thereby saving the capacity of the memory. When a resonance index is to be specified in addition to the cutoff frequency, filter coefficients corresponding to two difference resonance indexes are acquired by the interpolation, then a new filter coefficient is acquired by executing the interpolation referring to these two filter coefficients.

Abstract: An electrical musical instrument includes a scale designator for sequentially and automatically designating a scale on the basis of prestored data of a music piece, and a musical tone signal generator for outputting a musical tone signal including a harmonic frequency on the basis of the scale designated by said scale designator or as a fundamental frequency. A voice detector detects an external voice and the detected voice is divided by a modulator into voice signals in a plurality of frequency ranges. The musical tone signal is modulated in units of corresponding frequency ranges on the basis of the voice signals divided into the plurality of frequency ranges.

Abstract: A filter calculating section has a plurality of basic filters formed on a time-divisional basis. The timbre of a musical tone signal is controlled by a memory section, an accumulator, a selector, an I/O assign section and a control section using the basic filters formed by the filter calculating section. A digital filter coefficient stored in a digital filter coefficient memory is read out using integer data output from a cutoff controller as an address. An interpolation circuit interpolates this digital filter coefficient on the basis of fraction data output from the cutoff controller. Based on the interpolated digital filter coefficient, the timbre of a musical tone signal is controlled.

Abstract: A guitar control system using multiple string processing channels for developing pitch and peak signals for a multiple of string vibrations. Pitch data is multiplexed into a microprocessor along with the peak data and the programmed microprocessor outputs processed sound information on an address/data buss. Midi input/output, analog input/output and counter circuitry are interactively connected with the data buss, and final audio processing is derived from the analog output.

Abstract: A musical tone synthesizing apparatus has a closed-loop configuration including an adder, a filter and a delay circuit. The adder adds its feedback signal to a signal to be synthesized which is applied from an external device. The filter constructed as the all-pass filter has a frequency characteristic by which a phase delay between its input and output signals is varied in response to a frequency variation of its input signal. Such all-pass filter includes a delay element having a delay time which is set longer than a predetermined unit delay time corresponding to a sampling period to be employed. Herein, the output of adder is fed back to the adder via the all-pass filter and delay circuit as the feedback signal. Thus, a signal circulating the closed-loop is picked up as a synthesized musical tone signal.

Abstract: A musical tone synthesizing apparatus is disclosed wherein an excitation signal corresponding to performance data is generated and supplied to a loop circuit. In the loop circuit, this excitation signal is delayed for at least a fixed time period and a repeatedly circulating muscial tone signal is generated. At the beginning of the generation of this musical tone signal, a initial signal with a frequency which corresponds to the pitch of the generated musical tone is supplied. As a result of this, in the loop circuit, resonant operation is carried out quickly in accordance with the initial signal.

Abstract: A musical tone waveform signal generating apparatus is used to generate the waveform signal full of variety which simulates the sound waveform of wind instrument. This apparatus provides a loop including first and second signal lines through which the waveform signal is circulated. Both of first and second signal lines are connected to a conversion portion which receives the waveform signal from the second signal line and a musical tone control signal which is used to control a musical parameter of a musical tone to be generated. The conversion portion effects the predetermined non-linear conversion on the waveform signal in response to the musical tone control signal so that a converted waveform signal to be obtained from the conversion portion is to be outputted to the first signal line.

Abstract: A method and apparatus are disclosed for the dynamic control of a MIDI synthesizer filter. A digital filter controlled by a plurality of filter coefficients is preferably coupled to the output of an excitation signal source within a MIDI synthesizer. The excitation signal source is typically controlled by a MIDI data file comprising a sequential series of program control commands and matching note on and note off commands. A plurality of filter coefficient factors are stored in memory and periodically accessed in response to variations in the program control commands and matching note on and note off commands. The selected filter coefficient factors are then utilized to calculate appropriate filter coefficients so that the center frequency and filter Q of the digital filter may be dynamically and optimally controlled.

Abstract: A melody generating system is fabricated from a switch unit operative to produce an activation signal, an analog signal producing unit responsive to the activation signal and producing an analog melody signal carrying pieces of melody information used for reproducing a melody and a sound unit responsive to the analog melody signal for reproducing the melody, wherein the analog signal producing unit comprises an analog signal producing circuit integrated on a single semiconductor chip and responsive to the activation signal for producing a read out controlling signal and a memory circuit storing the pieces of melody information and responsive to the read out controlling signal for producing a digital melody information carrying signal, and the analog signal producing circuit is further responsive to the digital melody information carrying signal for producing the analog melody signal, so that a system supplier easily copes with a request for a new melody by changing the pieces of melody information stored in t

Abstract: An analog signal synthesizing apparatus includes a waveform memory for storing a plurality of analog signals as PCM data sampled with different sampling frequencies, the amount of PCM data corresponding to plural channels being read from the waveform memory and used to synthesize the analog signals. The analog signal synthesizing apparatus includes an oversampling device for shifting the sampling frequency of the PCM data read from the waveform memory for each channel toward the side of high frequency; a summing device for summing the oversampled PCM data for the respective channel; a D/A converter for converting the summed data into an analog signal; and a low-pass filter for setting a cut-off frequency based on the sampling frequency shifted to the side of high frequency and for eliminating aliasing noises included in the PCM data from the synthesized analog signal. The elimination of the aliasing noises included in the PCM data for each channel is carried out at the common low-pass filter.

Abstract: A musical sound analyzer and synthesizer uses a model that considers a sound to be composed of two types of elements: a deterministic component plus a stochastic component. The deterministic component is represented as a series of sinusoids, with an amplitude and a frequency function for each sinusoid. The stochastic component is represented as a series of magnitude spectral envelopes. From this representation, sounds can be synthesized that, in the absence of modifications, can behave as perceptual identities, that is, they are perceptually equal to the original sound. In addition, stored representations of sounds can be easily modified in a musical synthesizer to create a wide variety of new sounds.

Abstract: A guitar control system using multiple string processing channels for developing pitch and peak signals for a multiple of string vibrations. Pitch data is multiplexed into a microprocessor along with the peak data and the programmed microprocessor outputs processed sound information on an address/data buss. Midi input/output, analog input/output and counter circuitry are interactively connected with the data buss, and final audio processing is derived from the analog output.

Abstract: A tone generation control unit has four waveform read/write channels for selectively the reading or writing data in a waveform memory. A plurality of waveform signals stored in the waveform memory are converted into analog signals to be subjected to timbre and tone volume control through voltage-controlled filters and voltage-controlled amplifiers before being fed to a mixing adder. An output signal of the mixing adder is converted into a digital signal which is stored in the waveform memory again through processing of the tone generation control unit. The stored converted output from the mixing adder is later used again as a new sound source waveform which is operated on to produce tones.

Abstract: Waveform data is read out from a memory which stores the waveform data at a rate corresponding to a designated pitch. The readout data is supplied to digital filters, and two or more different filtering operations are executed in the digital filters. Two or more waveform data obtained as a filtering result are synthesized at a rate determined in response to a breath input signal output from a breath sensor, and the synthesized data is output as a musical tone waveform signal. The filter performs the filtering operation while a cut-off frequency is changed in response to the breath input signal.

Abstract: In an apparatus for modulation of the timbre of an electrical amplifier, in particular for guitars, a cylindric coil (2), which can be disposed downstream of an amplifier output, and a bar magnet (3) inside the cylindric coil (2), which can be deflected against restoring forces within a limited amplitude range out of its position of equilibrium, are provided for achieving a tonal effect corresponding to the direct connection of a loudspeaker.

Abstract: A circuit for adding a resonance tone to a tone signal to be generated is provided. When a damper operator is not operated, the resonance tone is not added but an ordinary tone signal is generated. When the damper operator has been operated, the resonance tone is added so that a tone signal including the resonance tone is generated. An effect of a damper operator, i.e., loud pedal, in a piano, a natural musical instrument, is thereby simulated with high fidelity. The resonance tone may be produced by passing an ordinary tone signal through a filter. Alternatively, data obtained by sampling an actually produced tone of a piano, a natural musical instrument, when a damper operator, i.e., loud pedal, is ON may be stored in a memory and a resonance tone may be generated by reading out the stored data from the memory. The signal of the generated resonance tone may be sounded by itself or after mixing with an ordinary tone signal at a suitable mixing ratio.

Abstract: At least two sets of filter coefficients corresponding to different filter characteristics are interpolated by using a control signal for controlling tone color as a parameter of interpolation. Filter coefficients obtained by the interpolation are supplied to a digital filter to determine its filter characteristics and an input tone signal is modified in accordance with the filter characteristics thus determined. Filter characteristics of diverse variation as compared with the number of prepared filter coefficients can thereby be realized. Further, timewise change of filter characteristics can be realized by changing a parameter of interpolation with lapse of time or changing two sets of filter coefficients to be interpolated with lapse of time. Designation of filter coefficients can be made by designating coordinate data of coordinates having at least two axes.

Abstract: The tone signal from a transducer monitoring the music vibrations of a bowed musical instrument contains an objectionable friction noise component which is removed by passing the tone signal through a high-pass filter having a variable cutoff frequency which is controlled by a pitch detector monitoring the fundamental frequency of a played note in the tone signal. The cutoff frequency of the filter is kept slightly below the fundamental frequency of the played note to avoid altering the tone color of the tone signal. When no fundamental frequency is detected by the pitch detector, the cutoff frequency of the filter remains at a pre-determined minimum which may be adjustable by the musician for best effect when strings are both bowed and plucked. The filtered tone signal may be applied to the pitch detector in order to increase the accuracy of the pitch detection process and thus increase the accuracy of the noise reducing characteristics of the system.

Abstract: In a typical musical tone producing device of a full waveshape readout type, a full waveshape of a musical tone to be produced from the start to the end of sounding or a rise portion and a part of the waveshape following the rise portion of the musical tone is stored in a waveshape memory, and the musical tone is formed by reading out the waveshape from the waveform memory once, or reading out the rise portion once and thereafter reading out the partial waveshape repeatedly. A digital filter is introduced following the waveshape memory in this tone producing device. The filter characteristics are determined in accordance with a tone color change parameter such as the key touch or the tone pitch of the musical tone, thereby realizing a tone color change of the musical tone. Further, in order to realize timewise change of tone color of the musical tone, the circuit which has the tone color change parameter vary with time is proposed.

Abstract: A pitch synchronizing signal snychronized with the pitch of a digital tone signal to be filtered is generated by a pitch synchronizing signal generation circuit. A digital filter circuit which receives the digital tone signal and imparts it with a desired tone color by subjecting it to a proper filter operation executes this filter operation with a sampling period synchronized with the pitch synchronizing signal. A moving formant thereby is realized which is suitable for control of a tone. A pitch synchronization output circuit for sampling and outputting the output of the digital filter circuit in accordance with the pitch synchronizing signal may be provided and this will prevent occurrence of a sampling noise. A switching circuit is provided for enabling switching order of the digital filter circuit between an even number and an odd number. By this switching of order, a desired filter characteristic can be realized with high fidelity.

Abstract: In storing digital tone waveshape data in a waveshape memory, sampled tone waveshape data is stored in the memory by previously elevating the level of frequency components in a predetermined high frequency region. This predetermined high frequency region corresponds to a frequency region to which quantization noise components belong. The tone waveshape data stored in the waveshape memory in this manner has the signal level of the component of the region including the quantization noise components reinforced as compared with the original tone waveshape. The tone waveshape data read out from the waveshape memory is applied to a filter of a characteristic which restrains the level of the component in the predetermined high frequency region. The level of the quantization noise components belonging to the predetermined high frequency region contained in the tone waveshape data thereby is restrained.

Abstract: A time-changing coefficient digital filter having a data RAM for storing input data, a purality of N data registers at the output of the data RAM forming a delay element, a coefficient RAM storing coefficient values, coefficient registers temporarily storing respective coefficients, and a multiplier for multiplying data read out of data registers and coefficient registers respectively. Data from the multiplier and inputs is accumulated in an adder. Coefficient registers and data registers are updated by data from the data RAM and coefficient RAM. The coefficient digital filter provides a sum of products sequentially read out of the coefficient and data registers. The digital filter is applied to produce a musical instrumet having improved tonal qualities.

Abstract: Apparatus is disclosed whereby an electronic musical tone generator is controlled in response to a musical instrument using mechanically vibrated strings. A bank of digital note filters is associated with each string to find the closest true musical note frequency corresponding to the vibration frequency of the string. The filters operate by computing the autocorrelation function of the string's vibration waveshape and then performing a Fourier transform to obtain the identification of the closest true musical note. An efficient and simple implementation is disclosed for an analog-to-digital signal conversion, the computation of the autocorrelation, and the Fourier transform. Provision is made for introducing frequency changes corresponding to a pitch bend in the vibration frequencies of the string.

Abstract: For electronically reproducing the total sound produced by a musical instrument, the musical instrument comprises a plurality of components each of which produces one aspect of the total sound, an electronic acoustic reproduction system comprises vibration transducer means mounted on the instrument for receiving the one aspect of the total sound from one of the components and transforming the one aspect to an electrical signal, and electronic filter means for processing the electrical signal to produce a total electrical signal representative of the total sound of the musical instrument.

Abstract: A tone signal generating apparatus comprises a waveform memory in which a plurality of waveform data representing different waveforms but corresponding to a same tone name are stored. These different waveform data are sequentially read from the memory and are supplied to a digital low-pass filter which comprises a delay circuit and a multiplier connected to each other to form a feedback loop. The low-pass filter smoothes abrupt variation of the waveform data and outputs a smoothed waveform data thereby interpolating the different waveforms. A tone signal is produced in accordance with this smoothed waveform data.

Abstract: In the production of a desired musical waveform by combining harmonic components corresponding to respective harmonic orders, each harmonic component value is controlled by a selected cut-off harmonic order qc, level Ha and slope of the formant filter characteristic. The cut-off harmonic order qc, the level Ha and the slope values can each be varied over a predetermined range. Therefore, the slope values of the formant filter characteristic are interpolated to raise resolution, by which it is possible to prevent an abrupt change in the formant filter characteristic and suppress the generation of noise.

Abstract: A musical tone signal generating apparatus generates a musical tone signal whose tone color can be changed independently of a pitch or a frequency of the musical tone signal. The musical tone signal generating apparatus comprises a shift register on which sampled data of a predetermined waveform are initially loaded. The sampled data in the shift register are shifted at a frequency corresponding to a rate of change of the tone color, and each sampled data shifted out of the shift register is subjected to a predetermined operation such as a multiplication by a predetermined coefficient and is fed back to the shift register. The sampled data in the stages of the shift register are selectively outputted by a selector controlled in accordance with selection control data formed based on the pitch of the musical tone so that the sampled data are outputted at a rate determined by the tone pitch. The musical tone signal is then formed based on the thus outputted sampled data.

Abstract: In a typical musical tone producing device of a full waveshape readout type, a full waveshape of a musical tone to be produced from the start to the end of sounding or a rise portion and a part of the waveshape following the rise portion of the musical tone is stored in a waveshape memory, and the musical tone is formed by reading out the waveshape from the waveform memory once, or reading out the rise portion once and thereafter reading out the partial waveshape repeatedly. A digital filter is introduced following the waveshape memory in this tone producing device. The filter characteristics is determined in accordance with a tone color change parameter such as the key touch or the tone pitch of the musical tone, thereby realizing a tone color change of the musical tone. Further, in order to realize timewise change of tone color of the musical tone, the circuit which has the tone color change parameter vary with time is proposed.

Abstract: A digital system is provided for synthesizing individual voices of musical instruments, which may then be combined into a musical composition. The system for a single voice is comprised of means for solving a system of simultaneous finite difference equations, where time is represented by real time in the computations. Musical sounds of the voice can then be produced by repetitiously solving the difference equations that model the instrument in real time, using an array of elemental means named "universal processing elements" (UPEs) interconnected by a matrix to each other and to external input and output terminals, and varying the sounds by varying the parameters. Each UPE is capable of computing Y=A+(B.times.M) from pipelined bit-serial inputs. The difference equations model a general linear filter, a second-order linear filter, a nonlinear polynomial function, and a random number (noise) generating function.

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 digital filter is provided between a tone signal generation circuit which supplies a digital tone signal in accordance with a first sampling frequency and a sampling circuit which resamples this digital tone signal in accordance with a second sampling frequency which is lower than the first sampling frequency. This digital filter filters the input digital tone signal with such amplitude-frequency characteristics as to be able to substantially remove an aliasing noise produced due to the second sampling frequency (e.g., with low-pass filter characteristics having a cut-off frequency which is 1/2 the second sampling frequency). This removes high frequency components producing an aliasing noise from the digital tone signal before it is applied to the resampling circuit whereby generation of the aliasing noise in resampling is prevented.

Abstract: An audio processing system for injecting left and right channel audio signals with a signal having a fundamental frequency component that is half the frequency of the highest amplitude low frequency component in the left and right channel audio signals. The left and right channel audio signals are combined to form a monaural signal that is low pass filtered and applied to a demodulator circuit. The demodulator circuit generates a control signal having a frequency that is half the frequency of the highest amplitude frequency component in the signal at the output of the band pass filter. The control signal varies the phase of the signal at the output of the band pass filter according to the polarity of the control signal. The resulting signal is selectively added to the left and right input signals.

Abstract: Disclosed is a real-time spectrum analyzer for monitoring acoustic energy, in particular a singer's formant, comprising a microphone element for converting the energy of a singer's voice to an electrical signal, band-pass filters for filtering the signal and selectively passing a portion thereof in a dedicated frequency range of from about 2500 to about 3500 Hz corresponding to singer's formant to a display meter responsive to the portion for visually displaying the magnitude of the total energy of said portion, the band-pass filters being connected in series and tuned to different center frequencies but overlapping from about 20% to about 60% of the total pass-band.

Abstract: A system for converting musical sounds into digital data for use with a electronic synthesizer. An infra red pitch sensor detects pitch of string vibration. Envelope of this signal is filtered and applied to a comparator with floating threshold. Square wave output of comparator is used to reset a continually running counter and latch valid data into a latch. Valid data is used as address for a memory which contains quantized values corresponding to standard musical notes. Transposition of keys may be accomplished in memory lookup table. Amplitude of input signal is detected by A/D converter, and with pitch information from memory lookup table is sent to processor. Processor makes decision when valid data is present, and when present outputs data to synthesizer.

Abstract: A first waveshape memory stores a full waveshape of a tone from the start to the end of sounding of the tone or a portion thereof in plural periods. A second waveshape memory stores waveshape data of a modification waveshape for the full waveshape or the portion thereof. A tone waveshape signal read out from the first waveshape memory and a modification waveshape signal read out from the second waveshape memory are both multiplied with respective coefficients whereby these waveshape signals are weighted. These weighted waveshape signals are added together to provide a mixed tone signal. By controlling the coefficients, the tone color imparted on the mixed signal is variously determined. The coefficients for the tone color control are provided in accordance with key scaling, key touch or operation states of control knobs. Thus, tone signals having a variety of tone color changes can be realized without the necessity of many wave memories.

Abstract: A sound interface circuit is implemented in large scale integrated circuitry (LSI) on a single chip to provide 3 voice electronic music synthesizer/sound effects, and is compatible with instructions from commercially available microprocessors; whereof a wide range, high-resolution control of pitch (frequency) tone color (harmonic content) and dynamics (volume) is achieved and specialized control circuitry minimizes software overhead, facilitating use in arcade/home video games and low cost musical instruments.

Abstract: A preamplifier adapted to receive audio frequency electrical signals generated by a musical instrument for providing controlled output signals therefrom having selected distortion and harmonic signal content is shown wherein the preamplifier includes an amplifier for amplifying audio frequency electrical signals generated by the musical instrument, a first electrical signal processing channel operatively coupled to the amplifier for receiving the amplified audio frequency electrical signals and for producing in response thereto a first controlled output signal wherein the first electrical signal processing channel includes a plurality of selectively interconnectable signal processing circuits at least one of which is capable of at least one of selectively amplifying, distorting and adding preselected harmonic content to the first controlled output signal, a second electrical processing channel operatively coupled to the amplifier for receiving the amplified audio electrical signals and for producing response

Abstract: An electronic musical instrument comprises a plurality of keyboards each having a plurality of keys, a control circuit for controlling a manner of tone production, and a musical tone production circuit responsive to respective depressed keys of respective keyboards. The control circuit controls the musical tone production circuit in response to operation of a switch mounted on a control panel for manually selecting one of a plurality of sets of preset parameters corresponding to a kind of a musical tone to be performed. The musical tone production circuit modifies a tone specified by a depressed key in any keyboard according to the selected switch on the control panel.

Abstract: For amplified musical instruments such as electric guitars, this method of extending the range of timbre variation available from a "wah" type of pedal controlled sound modification effect provides musicians with increased flexibility of expression by including within the controlling range of the foot pedal an unmodified "dry" condition in addition to the variable modified condition with the capability of blending smoothly back and forth between the two conditions.

Abstract: An electronic musical instrument is provided with a temporal variation circuit of SCF parameters for temporally varying the filter characteristic of a switched capacitor filter circuit, a control circuit for digitally controlling the temporal variation circuit and a touch response circuit for detecting, by scanning, touch response data in performance, whereby temporal variations of a musical waveform signal are digitally controlled.

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: A digital filter imparting a desired tone color to the tone signal is realized by the combination of a digital pole filter and a digital zero filter capable of controlling a pole and a zero in an amplitude-frequency characteristic respectively. The amplitude-frequency characteristic of the digital filter is a composite of the respective characteristics of the pole filter and the zero filter. A "peak" portion and a "valley" portion in this composite characteristic can be set independently by the pole control of the pole filter and the zero control of the zero filter, whereby the desired tone color characteristic can be readily realized. Further, the digital filter may comprise a plurality of digital filters having respective different constructions and a connection switching circuit capable of setting arbitrarily connection between these filters. The filter characteristic as a whole can be diversely altered by changing the connection, whereby diverse tone color characteristics can be realized with ease.

Abstract: An electronic musical instrument comprises a keyboard, a tone generator and a digital filter. The tone generator bit-serially generates a musical tone signal corresponding to a depressed key on the keyboard. The digital filter bit-serially performs a digital filtering operation of the musical tone signal in accordance with the predetermined amplitude-frequency characteristic. A musical tone is produced based on an output of the digital filter, whereby the characteristic is imparted to the musical tone. This bit-serial processing in the digital filter makes not only the circuit construction of the digital filter itself but also that of the electronic musical instrument incorporating this digital filter smaller and simpler.

Abstract: A tone generation system intended primarily for use in electronic musical instruments wherein a digital representation of a harmonically rich waveform is sampled, and a musical tone is produced therefrom. The stored waveform could be the four term Blackman-Harris window function, which has negligible side lobes and thus greatly attenuated higher harmonics. The stored function is read out at a fixed rate, but the time periods between successive readings of the waveform are varied to thereby vary the frequency of the output signal.

Abstract: An apparatus for encoding and decoding musical signals in digital form employs conversion to the frequency domain. Discrete Fourier transform coefficients are calculated from time domain digital data at selected frequencies which are organized in sets of octavely related frequencies. Selecting frequencies in this manner greatly reduces the data rate by eliminating coefficients for many higher frequencies without a great loss of fidelity because the provision of a predetermined number of frequencies in each octave approximates the tonal response of the human ear. A further refinement is selection of frequencies to correspond to the frequencies of musical notes where the greatest energy can be expected.

Abstract: An electronic musical instrument comprises a plurality of musical tone control units each having a tone waveform producing circuit, a volume envelope circuit, a filter circuit and other circuits. A given musical tone data can be preset in each musical tone control unit. Musical tone signals produced by the musical tone control units are synthesized to provide an effective musical tone.

Abstract: An electronic musical instrument comprising a tone generator, an accumulator and a digital filter. The tone generator generates musical tone signals each represented by sampled values, corresponding to depressed keys. The accumulator accumulates the sampled values of the musical tone signals at predetermined timings. The digital filter modifies an output of the accumulator in accordance with the amplitude-frequency characteristic of a predetermined formant characteristic. A musical tone is produced based on an output of the digital filter circuit, thereby the formant characteristic is imparted to the musical tone.This utilization of the digital filter for the musical instrument makes it possible to impart a formant characteristic to a musical tone without a complex circuit construction. Moreover the insertion of the accumulator following the tone generator makes it possible to use the digital filter of a low speed type.

Abstract: An audio signal processing system for producing a moving comb filter effect having an all pass phase filter or other suitable phase shifting device in a first input branch and a bypass circuit with an optional inverter in a second input branch. A frequency shifter is inserted either into the first or the second input branch. A first summing network is connected to the outputs of the first and second input branch. An optional second summing network is connected to the output of the first input branch and the inverted output of the second input branch. A feedback circuit may be connected between the output of one of the summing networks to the input of the system to enhance the moving comb filter effect. Also, at least one switching circuit may be used to obtain phase reversals in the frequency shifter thereby facilitating up or down detuning or successive up and down detunings of the comb filter frequencies.

Abstract: Apparatus for eliminating feedback in stage monitors for selected musical instruments includes filter networks for attenuation of a broad frequency range including the entire range of frequencies contributing to the feedback. A combination of high order low-pass and high-pass filters is used to pass fundamental and second order components of a selected instrument, while attenuating the undesired feedback frequencies as well as extremely low range frequencies capable of damaging a speaker. A pair of passbands is provided, and a pair of frequency bands is suppressed, the two pairs providing alternate attenuation and pass-bands. Active filters having operational amplifiers and frequency selective circuits are used, along with buffering and summing circuits, to attain the desired frequency characteristic.

Abstract: Apparatus for producing a chorale or vocal effect in an electronic musical instrument comprises means responsive to the playing keys of the instrument for producing an indexing signal and means responsive to the indexing signal for sequentially developing a plurality of control signals. A programmable filter is responsive to each sequentially developed control signal for modifying the harmonic content of a tone signal to simulate a different vowel-like sound for producing a vocal effect consisting of a sequence of different vowel-like sounds as the keys are played. The modified tone signal may be coupled through a chorus generator to simulate a chorale effect and the programmed characteristics of the filter may be modulated to further animate the performance as well as being made responsive to a glide signal for producing two different vowel-like sounds in succession at two different pitches in response to a glissando or portamento command.