System for generating tone source waveshapes

Abstract

The system comprises a frequency number memory device for storing information regarding the frequencies of respective tones, a keyboard switch for reading out frequency number information corresponding thereto from the memory device, an address generator including an adder for adding a predetermined number of the frequency number information thereby producing an address signal consisting of plural bits, address composers for processing the bits of the address signal and thereby composing digital tone signals constituting a saw-tooth, square and triangular waveshape, and digital-analog converters for converting the digital tone signals into analog tone signals, which are thereafter used to synthesize waveshapes of any tone.

What is claimed is: 
     
       1. A system for generating tone source waveshapes comprising a pre-loaded frequency number memory device which stores in digital representation a plurality of frequency numbers corresponding respectively to the fundamental frequencies of the notes of said waveshapes; a keyboard switch circuit having a key-actuated switch for each of said notes for reading out a frequency number respectively corresponding thereto from said frequency memory device; an address generator responsive to the frequency number read out from said frequency memory device for producing a given number of successive address signals periodically, each address signal consisting of a plurality of bits; at least one address composer connected to receive said successive address signals from said address generator directly and responsive to a predetermined number of said plurality of bits of each address signal in the range from one bit to n bits, where n is more than one and .[.less.]. .Iadd.not more .Iaddend.than the bit plurality, for digitally composing a tone waveshape having a fundamental frequency corresponding to said read out frequency number with an amplitude versus time characteristic determined by the digital word value of each predetermined number of address signal bits to which said one address composer responds; and means for converting the digitally composed tone waveshape into an analog equivalent thereof. 
     
     
       2. The system according to claim 1 wherein said address generator includes an adder for successively adding the read-out frequency number to itself and a buffer memory for storing the accumulated frequency number resulting from the successive addition performed by said adder. 
     
     
       3. The system according to claim 2 wherein said buffer memory stores said accumulated frequency number in the form of a plurality of bits, and said address composer comprises a buffer memory for storing a predetermined number of bits counting from the most significant bit in said address signal, thereby producing a saw-tooth wave. 
     
     
       4. The system according to claim 1 wherein said address composer is a duty variable square wave address generator. 
     
     
       5. The system according to claim 2 wherein said buffer memory stores said accumulated frequency number in the form of a plurality of bits and said address composer includes inverter means connected to receive only the most significant bit of said address signal, thereby producing a symmetrical square wave. 
     
     
       6. The system according to claim 2 wherein said buffer memory stores said accumulated frequency number in the form of a plurality of bits and said address composer comprises an AND gate circuit connected to receive the most significant bit of said address signal and a bit which is one bit less significant than said most significant bit, and inverter means responsive to the output of said AND gate circuit, thereby producing an asymmetrical square wave. 
     
     
       7. The system according to claim 2 wherein said buffer memory stores said accumulated frequency number in the form of a plurality of bits and wherein said address composer comprises a second buffer memory connected to receive a predetermined number of bits counting from the most significant bit in the address signal, inverter means, a selector for applying said predetermined number of the bits except the most significant bit and the bit which is one bit less significant than said most significant bit directly to and through said inverter means to said selector, means for controlling said selector in accordance with said bit which is one bit less significant than said most significant bit, complementing means responsive to the output from said selector for forming a two's complement, and means for controlling said complementing means in accordance with said most significant bit, thereby forming a triangular wave. 
     
     
       8. The system according to claim 1 which further comprises an attack-decay oscillator, an attack-decay logic circuit responsive to a signal indicating the operation of said key-actuated switch and the output from said attack-decay oscillator for producing an address signal, an attack-decay memory device storing information regarding attack and decay envelopes and connected to receive .[.said.]. .Iadd.the .Iaddend.address .[.signals.]. .Iadd.signal from the attack/decay logic circuit .Iaddend.for producing said attack and decay envelope information, and a multiplier connected between said address composer and said digital-analog converting means for multiplying said digital tone signal by said attack and decay envelope information. .Iadd. 9. In an electronic musical instrument having note selection keys, a system for generating tone source waveshapes comprising: key identification means having a key-actuated switch for each note for generating a key identification signal corresponding thereto;   address generator means responsive to the key identification signal for producing a given number of successive address signals periodically, each address signal consisting of a plurality of bits;   address composer means connected to receive said successive address signals from said address generator means, and responsive to a predetermined number of said plurality of bits of each address signal in the range from one bit to n bits where n is more than one and not more than the bit plurality, for digitally composing a tone waveshape having a fundamental frequency corresponding to said generated key identification signal with an amplitude versus time characteristic determined by the digital word value of each predetermined number of address signal bits to which said address composer means responds, said address composer means not utilizing a waveshape memory for said digital waveshape composition; and   means for converting the digitally composed tone waveshape into an analog equivalent thereof. .Iaddend. .Iadd. 10. The system according to claim 9 further comprising:   an attack-decay clock generator,   envelope information means, responsive to a signal indicating the opration of a key-actuated switch and to clock pulses from said attack-decay clock generator, for providing information regarding attack and decay envelopes, and   waveform modification means, cooprating with said envelope information means and said address composer means, for modifying said digitally composed waveshape in accordance with said information regarding attack and decay envelopes. .Iaddend. .Iadd. 11. A system for generating tone source waveshapes comprising:   means for generating key identification signals in digital representation corresponding respectively to note-related fundamental frequencies of said waveshapes;   a keyboard switch circuit having a key-actuated switch for each of said notes for actuating said generating means to generate the key identification signal corresponding thereto;   an address generator responsive to the key identification signal for producing a given number of successive address signals periodically, each address signal consisting of a plurality of bits;   an address composer, connected to receive said successive address signals from said address generator and responsive to a predetermined number of said plurality of bits of each address signal in the range from one bit to n bits where n is more than one and not more than the bit plurality, for digitally composing a tone waveshape solely by carrying out arithmetic and/or logical operations directly on said predetermined number of address signal bits, said tone waveshape having a fundamental frequency corresponding to said generated key identification signal with an amplitude versus time characteristic determined by the digital word value of each predetermined number of address signal bits to which said address composer responds; and   means for converting the digitally composed tone waveshape into an analog equivalent thereof. .Iaddend. .Iadd. 12. The system according to claim 11 which further comprises an attack-decay oscillator, an attack-decay logic circuit responsive to a signal indicating the operation of said key-actuated switch and the output from said attack-decay oscillator for producing an address signal, an attack-decay memory device storing information regarding attack and decay envelopes and connected to receive the address signal from the attack-decay logic circuit for producing said attack and decay envelope information, and a multiplier connected between said address composer and said digital-analog converting means for multiplying said digital tone signal by said attack and decay envelope information. .Iaddend. .Iadd. 13. An electronic musical instrument comprising:   means for producing a set of digital addresses which progress through a fixed range of values in a certain time interval corresponding to the period of a selected musical note, and   digital logic circuitry means for forming waveform sample point amplitude values, without the use of a waveform memory, by manipulation of the digital address values themselves, said manipulation being carried out in unison with the progressive changes in digital address value so that the resultantly formed musical waveform has the period of said selected note. .Iaddend..Iadd. 14. An electronic musical instrument according to claim 13 further comprising:   a keyboard, said selected musical note being selected by actuation of a key,   an attack-decay clock generator,   envelope information means, responsive to said key actuation and to clock pulses from said generator, for providing information regarding attack and decay envelopes, and   waveform modification means, cooperating with said envelope information means and said digital logic circuitry means, for modifying said manipulation in accordance with said information regarding attack and decay envelopes. .Iaddend..Iadd. 15. An electronic musical instrument according to claim 13 wherein said manipulation consists of logical manipulation. .Iaddend. .Iadd. 16. An electronic musical instrument according to claim 13 wherein said manipulation consists of arithmetic manipulation. .Iaddend..Iadd. 17. An electronic musical instrument according to claim 13 wherein said manipulation consists of combined logical and arithmetic manipulation. .Iaddend.