Note frequency generator for an electronic musical instrument

Claim 2

In combination with a keyboard musical instrument having a waveshape memory storing a plurality of data words corresponding to the amplitudes of a corresponding number of evenly spaced points defining a cycle of an audio musical signal and in which said data words are sequentially and repetitively read out of the waveshape memory and transferred to a digital-to-analog converter at an average rate proportional to the pitch of the musical tone being generated wherein said average rate is generated by a non-integer frequency divider, apparatus for reducing undesired frequency components produced by said non-integer frequency divider comprising; a waveshape memory storing in memory locations said plurality of data words, a frequency number means for providing digitally coded values corresponding to the fundamental frequencies of musical notes produced by said musical instrument, a first clock means for providing timing clock pulses, assignor means whereby a frequency number is accessed from said frequency number means in response to an actuated key on said keyboard, an adder-accumulator means, operative at each timing clock pulse from said first clock means, wherein said frequency number accessed by said assignor means is added to the contents of said adder-accumulator and wherein the adder-accumulator generates an overflow signal whenever the accumulated value exceeds the capacity of the accumulator, a first addressing means whereby a sequence of M consecutive data words are cyclically and repetitively addressed out from said waveshape memory and wherein the waveshape memory location of the first data word in said sequence of consecutive data words is advanced by said overflow signal, a smoothing memory storing smoothing function data values, a second addressing means responsive to the contents of said adder-accumulator means whereby a sequence of smoothing function data values equal in number to said number M are addressed out from said smoothing memory, a plurality of multiplying means, each corresponding to one of said plurality of M data words addressed out from said waveshape memory, wherein said addressed data words are multiplied by said smoothing function data values addressed out from said smoothing memory, a summing means for adding all the product values provided by said plurality of multiplying means to generate an output data set and thereby reducing said undesired frequency components, and a signal conversion means wherein the output of said summing means is converted to an analog signal.

Claim 3

A musical instrument according to claim 1 wherein said smoothing function memory stores smoothing function data values computed according to the relation x.sub.n =sin(πn/M)/(πn/M) where n is the index corresponding to a data word location in said smoothing function memory and M is the number of data values in said plurality of data words addressed out from said waveshape memory.

Claim 4

A musical instrument according to claim 1 wherein said smoothing function memory stores smoothing function data values computed from values of the Bessel function J O (A) for increments of A equal to 2.4083/M where M is the number of data values in said plurality of data words addressed out from said waveshape memory.

Claim 5

A musical instrument according to claim 1 wherein said smoothing memory comprises a shift register operated in an end-around mode in which data values shifted to the register output are rewritten as input data values.

Claim 6

In combination with a keyboard musical instrument having a waveshape memory storing a plurality of K data words corresponding to the amplitudes of a corresponding number of evenly spaced points defining a cycle of an audio musical signal and in which said data words are sequentially and repetitively read out of the waveshape memory and transferred to a digital-to-analog converter at an average rate proportional to the pitch of the musical tone being generated wherein said average rate is generated by a non-integer frequency divider, apparatus for reducing undesired frequency components produced by said non-integer frequency divider comprising; a waveshape memory storing said plurality of K data words, a frequency number means for providing digitally coded values corresponding to the fundamental frequencies of musical notes produced by said musical instrument, a first clock means for providing timing clock pulses, assignor means whereby a frequency number is accessed from said frequency number means in response to an actuated key on said keyboard, an adder-accumulator means, operative at each timing clock pulse from said first clock means, wherein said addressed out frequency number is added to the sum previously contained in said adder-accumulator and wherein the adder-accumulator generates an overflow signal whenever the accumulated value exceeds the capacity the accumulator, a second clock means for providing shift clock pulses, a data memory, digit select circuitry responsive to said overflow signal wherein a predetermined number of the most significant bits are selected from the contents of said adder-accumulator means and stored in said data memory, pulse selection circuitry responsive to said oerflow signal for selecting a consecutive number of K-M+N clock pulses from said second clock means where K is equal to said plurality of data words in said waveshape memory, M is the current value of the most significant bits selected by said digit select circuitry, and N is the value of said most significant bits stored in said data memory, a first addressing means responsive to said overflow signal whereby a plurality of H data words are addressed out in sequence from said waveshape memory, where the address of the first data word in said sequence is advanced by said overflow signal, and H is a number not larger than said number K, a smoothing memory storing smoothing function data values, a second addressing means whereby a sequence of smoothing function data values equal in number to said number H are addressed out from said smoothing memory and wherein the memory address of the start of said sequence smoothing function data values is responsive to said selected number of K-M+N clock pulses, a plurality of multiplying means, each corresponding to one of said plurality of H data words addressed out from said waveshape memory, wherein said data words are multiplied by said smoothing function data values addressed out from said smoothing memory, a summing means for adding all the product values provided by said plurality of multiplying means and thereby reducing said undesired frequency components, and a signal conversion means wherein the output of said summing means is converted to an analog signal.

Claim 7

In combination with a keyboard musical instrument having a waveshape memory storing a plurality of K data words corresponding to the amplitudes of a corresponding number of evenly spaced points defining a cycle of an audio musical signal and in which said data words are sequentially and repetitively read out of the waveshape memory and transferred to a digital-to-analog converter at an average rate proportional to the pitch of the musical tone being generated wherein said average rate is generated by a non-integer frequency divider, apparatus for reducing undesired frequency components produced by said non-integer frequency divider comprising; a waveshape memory storing said plurality of K data words, a frequency number means for providing digitally coded values corresponding to the fundamental frequencies of musical notes produced by said musical instrument, a first clock means for providing timing clock pulses, assignor means whereby a frequency number is accessed from said frequency number means in response to an actuated key on said keyboard, an adder-accumulator means, operative at each timing clock pulse from said first clock means, wherein said addressed out frequency number is added to the sum previously contained in said adder-accumulator and wherein the adder-accumulator generates an overflow signal whenever the accumulated value exceeds the capacity the accumulator, a second clock means for providing shift clock pulses, a data memory, digit select circuitry responsive to said overflow signal wherein a predetermined number of the most significant bits are selected from the contents of said adder-accumulator means and stored in said data memory, pulse selection circuitry responsive to said oerflow signal for selecting a consecutive number of K-M+N clock pulses from said second clock means where K is equal to said plurality of data words in said waveshape memory, M is the current value of the most significant bits selected by said digit select circuitry, and N is the value of said most significant bits stored in said data memory, a first addressing means responsive to said overflow signal whereby a plurality of H data words are addressed out in sequence from said waveshape memory, where the address of the first data word in said sequence is advanced by said overflow signal, and H is a number not larger than said number K, a smoothing memory storing smoothing function data values, a second addressing means whereby a sequence of smoothing function data values equal in number to said number H are addressed out from said smoothing memory and wherein the memory address of the start of said sequence smoothing function data values is responsive to said selected number of K-M+N clock pulses, a plurality of multiplying means, each corresponding to one of said plurality of H data words addressed out from said waveshape memory, wherein said data words are multiplied by said smoothing function data values addressed out from said smoothing memory, a summing means for adding all the product values provided by said plurality of multiplying means and thereby reducing said undesired frequency components, and a signal conversion means wherein the output of said summing means is converted to an analog signal.

Claim 8

A musical instrument according to claim 1 wherein said smoothing function memory comprises a bi-directional shift register operated in an end-around mode attained by causing output data to be written as input data and wherein the shift direction is responsive to a shift control signal.

Claim 9

A musical instrument according to claim 6 wherein said pulse selection circuitry further comprises; sign detector circuitry for determining the algebraic sign of said quantity M-N and wherein a forward shift control signal is provided to said smoothing function memory if M-N is a positive number and whererein a backward shift control signal is provided if M-N is a negative number.

Claim 10

A musical instrument according to claim 6 wherein said frequency number means comprises an addressable memory storing digitally coded values corresponding to the frequencies of musical notes produced by said musical instrument.

Claim 11

In combination with a keyboard musical instrument having a waveshape memory storing a plurality of K evenly spaced points defining a cycle of a musical waveshape and in which said data words are sequentially and repetitively read out of the waveshape memory and transferred to a digital-to-analog converter at an average rate proportional to the pitch of the musical tone being generated wherein said average rate is generated by a noninteger frequency divider, apparatus for reducing frequency components produced by the noninteger frequency divider comprising; a waveshape memory storing said plurality of K data words, a frequency number means for providing binary digitally coded values of frequency numbers corresponding to the fundamental frequencies of musical notes produced by said musical instrument, a first clock means for providing timing clock pulses, assignor means whereby a binary digitally coded frequency number is accessed out fromm said frequency number means in response to an actuated key on said keyboard, an adder-accumulator means, operative at each timing clock pulse from said clock means, wherein said accessed binary digitally coded frequency number is added to the sum previously contained in said adder-accumulator and wherein the adder accumulator generates an overflow signal whenever a change occurs in the state of a preselected bit position of said sum, a first addressing means responsive to contents of said adder-accumulator means whereby a data word is addressed out from said waveshape memory in response to said overflow signal, a plurality of data storage means, of number H, storing said data words addressed out from said waveshape memory wherein the selection of the first data storage means in said cyclic order is advanced in response to said overflow signal, a smoothing memory storing smoothing function data values, a second addressing means responsive to the contents of said adder-accumulator means whereby smoothing function data values equal in number to said number H are addressed out in sequence from said smoothing memory, and wherein the address of the first one of said sequence of smoothing function data values is determined by said contents of said adder-accumulator means, a plurality of multiplying means, each corresponding to one of said plurality H of data storage means, wherein the contents of said data storage means are multiplied by said smoothing function data words addressed out from said smoothing memory, a summing means for adding all the product values provided by said plurality of multiplying means to generate an output data set and thereby reducing said undesired frequency components, and a signal conversion means wherein the output from said summing means is converted to an analog signal.

Claim 12

In combination with a keyboard musical instrument having a waveshape memory storing a plurality of K evenly spaced points defining a cycle of a musical waveshape and in which said data words are sequentially and repetitively read out of the waveshape memory and transferred to a digital-to-analog converter at an average rate proportional to the pitch of the musical tone being generated wherein said average rate is generated by a noninteger frequency divider, apparatus for reducing frequency components produced by the noninteger frequency divider comprising; a waveshape memory storing said plurality of K data words, a frequency number means for providing binary digitally coded values of frequency numbers corresponding to the fundamental frequencies of musical notes produced by said musical instrument, a first clock means for providing timing clock pulses, assignor means whereby a binary digitally coded frequency number is accessed out fromm said frequency number means in response to an actuated key on said keyboard, an adder-accumulator means, operative at each timing clock pulse from said clock means, wherein said accessed binary digitally coded frequency number is added to the sum previously contained in said adder-accumulator and wherein the adder accumulator generates an overflow signal whenever a change occurs in the state of a preselected bit position of said sum, a first addressing means responsive to contents of said adder-accumulator means whereby a data word is addressed out from said waveshape memory in response to said overflow signal, a plurality of data storage means, of number H, storing said data words addressed out from said waveshape memory wherein the selection of the first data storage means in said cyclic order is advanced in response to said overflow signal, a smoothing memory storing smoothing function data values, a second addressing means responsive to the contents of said adder-accumulator means whereby smoothing function data values equal in number to said number H are addressed out in sequence from said smoothing memory, and wherein the address of the first one of said sequence of smoothing function data values is determined by said contents of said adder-accumulator means, a plurality of multiplying means, each corresponding to one of said plurality H of data storage means, wherein the contents of said data storage means are multiplied by said smoothing function data words addressed out from said smoothing memory, a summing means for adding all the product values provided by said plurality of multiplying means to generate an output data set and thereby reducing said undesired frequency components, and a signal conversion means wherein the output from said summing means is converted to an analog signal.

Claim 13

In combination with a musical instrument having a waveshape memory storing a plurality of data words corresponding to the amplitude of K evenly spaced points defining a cycle of a musical waveshape and in which said data words are sequentially and repetitively read out of the waveshape memory at an average rate proportional to the pitch of the musical tone being generated wherein said average rate is generated by a noninteger frequency divider, apparatus for reducing frequency components produced by the noninteger frequency divider in the audible output musical signal comprising; a first clock means for providing timing clock signals, a waveshape memory storing said plurality of K data words, a frequency number generating means wherein a digitally coded value is created corresponding to the fundamental frequencies of musical notes produced by said musical instrument, assignor means whereby a frequency number is selected from said frequency number generating means in response to an actuated key on said keyboard, an adder-accumulator means, operative at each timing clock signal from said first clock means, wherein said selected frequency number is added to the sum previously contained in the adder accumulator and wherein the adder-accumulator generates an overflow signal whenever a change occurs in the state of a preselected bit position, a waveshape memory addressing means responsive to contents of said adder-accumulator means for addressing out data words from said waveshape memory in response to said overflow signal, a signal conversion means whereby data words addressed out of said waveshape memory are converted into analog signals, a filter means wherein a preselected consecutive number of said data words converted by said conversion means are stored in sequence and individually weighted and summed thereby reducing said undesired frequency components, and wherein each such data word addressed out of said waveshape memory is stored and a previously stored data word is discarded, and a signal utilization means comprising a sound system for converting the summed output from said filter means into an audible musical sound.

Claim 14

In combination with a musical instrument having a waveshape memory storing a plurality of data words corresponding to the amplitude of K evenly spaced points defining a cycle of a musical waveshape and in which said data words are sequentially and repetitively read out of the waveshape memory at an average rate proportional to the pitch of the musical tone being generated wherein said average rate is generated by a noninteger frequency divider, apparatus for reducing frequency components produced by the noninteger frequency divider in the audible output musical signal comprising; a first clock means for providing timing clock signals, a waveshape memory storing said plurality of K data words, a frequency number generating means wherein a digitally coded value is created corresponding to the fundamental frequencies of musical notes produced by said musical instrument, assignor means whereby a frequency number is selected from said frequency number generating means in response to an actuated key on said keyboard, an adder-accumulator means, operative at each timing clock signal from said first clock means, wherein said selected frequency number is added to the sum previously contained in the adder accumulator and wherein the adder-accumulator generates an overflow signal whenever a change occurs in the state of a preselected bit position, a waveshape memory addressing means responsive to contents of said adder-accumulator means for addressing out data words from said waveshape memory in response to said overflow signal, a signal conversion means whereby data words addressed out of said waveshape memory are converted into analog signals, a filter means wherein a preselected consecutive number of said data words converted by said conversion means are stored in sequence and individually weighted and summed thereby reducing said undesired frequency components, and wherein each such data word addressed out of said waveshape memory is stored and a previously stored data word is discarded, and a signal utilization means comprising a sound system for converting the summed output from said filter means into an audible musical sound.

Claim 15

A musical instrument according to claim 10 wherein said frequency number generating means comprises a memory storing digitally coded values corresponding to the fundamental frequencies of musical notes produced by said musical instrument.

Claim 16

A musical instrument according to claim 10 wherein said filter comprises a charge coupled device having a plurality of output signal ports which scale each stored value according to the relation x n =sin(n/N)/(n/N) where n is the index corresponding to a memory position in the charge coupled device, and N is said number of said plurality of data words.

Claim 17

A musical instrument according to claim 10 wherein said filter comprises a charge coupled devicice having a plurality of output signal ports which scale each stored value according to values computed from the Bessel function J O (A) for increments of A equal to 2.4083/N where N is the number of data values in said plurality of data words.

Claim 18

In combination with a musical instrument having a waveshape memory storing a plurality of data words corresponding to the amplitude of K evenly spaced points defining a cycle of a musical waveshape and in which said data words are sequentially and repetitively read out of the waveshape memory at an average rate proportional to the pitch of the musical tone being generated wherein said average rate is generated by a noninteger frequency divider, apparatus for reducing frequency components produced by the noninteger frequency divider in the audible output musical signal comprising; a first clock means for providing timing clock signals, a waveshape memory storing said plurality of K data words, a frequency number generating means wherein a digitally coded value is created corresponding to the fundamental frequencies of musical notes produced by said musical instrument, assignor means whereby a frequency number is selected from said frequency number generating means in response to an actuated key on said keyboard, an adder-accumulator means, operative at each timing clock signal from said first clock means, wherein said selected frequency number is added to the sum previously contained in the adder-accumulator and wherein the adder-accumulator generates an overflow signal whenever a change occurs in the state of a preselected bit position, a waveshape memory addressing means responsive to contents of said adder-accumulator means for addressing out data words from said waveshape memory in response to said overflow signal, a signal conversion means whereby data words addressed out of said waveshape memory are converted into analog signals, a filter means wherein a preselected number of said data words converted by said conversion means are stored and individually weighted and summed thereby reducing said undesired frequency components, a second clock means for providing shift clock pulses, digit select circuitry responsive to said overflow signal wherein a predetermined number of the most significant bits are selected from the contents of said adder-accumulator means, pulse selection circuitry responsive to said overflow signals for selecting a number of said shift clock pulses equal in number to said most significant bits selected by said digit select circuitry, signal advance circuitry responsive to said selected shift clock pulses for shifting data contained in said filter means, and a signal utilization means comprising a sound system for converting the summed output from said filter means into an audible musical sound.

Claim 19

In combination with a musical instrument having a waveshape memory storing a plurality of data words corresponding to the amplitude of K evenly spaced points defining a cycle of a musical waveshape and in which said data words are sequentially and repetitively read out of the waveshape memory at an average rate proportional to the pitch of the musical tone being generated wherein said average rate is generated by a noninteger frequency divider, apparatus for reducing frequency components produced by the noninteger frequency divider in the audible output musical signal comprising; a first clock means for providing timing clock signals, a waveshape memory storing said plurality of K data words, a frequency number generating means wherein a digitally coded value is created corresponding to the fundamental frequencies of musical notes produced by said musical instrument, assignor means whereby a frequency number is selected from said frequency number generating means in response to an actuated key on said keyboard, an adder-accumulator means, operative at each timing clock signal from said first clock means, wherein said selected frequency number is added to the sum previously contained in the adder-accumulator and wherein the adder-accumulator generates an overflow signal whenever a change occurs in the state of a preselected bit position, a waveshape memory addressing means responsive to contents of said adder-accumulator means for addressing out data words from said waveshape memory in response to said overflow signal, a signal conversion means whereby data words addressed out of said waveshape memory are converted into analog signals, a filter means wherein a preselected number of said data words converted by said conversion means are stored and individually weighted and summed thereby reducing said undesired frequency components, a second clock means for providing shift clock pulses, digit select circuitry responsive to said overflow signal wherein a predetermined number of the most significant bits are selected from the contents of said adder-accumulator means, pulse selection circuitry responsive to said overflow signals for selecting a number of said shift clock pulses equal in number to said most significant bits selected by said digit select circuitry, signal advance circuitry responsive to said selected shift clock pulses for shifting data contained in said filter means, and a signal utilization means comprising a sound system for converting the summed output from said filter means into an audible musical sound.