Digital tone generation system utilizing fixed duration time functions
First Claim
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1. An electronic musical instrument comprising:
- player actuated tone frequency selection means, memory means for storing one cycle of a fixed width window function waveform, means responsive to the actuation of the tone selection means for reading said waveform out of said memory at a fixed rate for each cycle thereof independent of the frequency selected and in a repetitive fashion to produce a continuous signal wherein the period of dead time between each successive reading of a cycle of the waveform is selectively adjusted in response to the frequency selected by the tone selection means without changing the width of the read out waveform to thereby produce a continuous train of time sequential said window function waveforms having a frequency inversely inversely proportional to the period of dead time between the commencement of each successive reading, and means responsive to the train of read out waveforms for producing an audible musical tone.
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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.
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Citations
16 Claims
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1. An electronic musical instrument comprising:
- player actuated tone frequency selection means, memory means for storing one cycle of a fixed width window function waveform, means responsive to the actuation of the tone selection means for reading said waveform out of said memory at a fixed rate for each cycle thereof independent of the frequency selected and in a repetitive fashion to produce a continuous signal wherein the period of dead time between each successive reading of a cycle of the waveform is selectively adjusted in response to the frequency selected by the tone selection means without changing the width of the read out waveform to thereby produce a continuous train of time sequential said window function waveforms having a frequency inversely inversely proportional to the period of dead time between the commencement of each successive reading, and means responsive to the train of read out waveforms for producing an audible musical tone.
- View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. An electronic musical instrument comprising:
- a keyboard comprising a plurality of playing keys assigned to different tone frequencies, memory means for storing one cycle of a window function waveform, means responsive to the actuation of any key of the keyboard for reading said waveform out of said memory at a fixed rate for each read out cycle thereof to produce a read out waveform of a predetermined constant width and in a repetitive fashion to produce a continuous train of said window functions separated by dead spaces as long as said any one key is held actuated and for adjusting the period of time between the beginning of each reading of the waveform and the beginning of the next reading thereof in the continuous signal in response to the tone frequency of the actuated key without changing the width of the read out waveform from said predetermined constant width, and means responsive to the read out window function waveforms for producing an audible musical tone.
- View Dependent Claims (11, 12, 13, 14)
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15. The method of generating a plurality of musical tones of differing frequency comprising:
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providing a memory in which one cycle of a fixed duration window function waveform is stored, actuating a tone frequency selection device to select a tone of a predetermined selective frequency and reading the stored waveform out of the memory at a fixed rate for each cycle thereof independent of the frequency selected and in a repetitive fashion to produce a continuous signal of the selected frequency, changing the tone selected by the tone frequency selection device, and in response to the changing of the tone frequency selected, selectively adjusting the period of dead time between each successive reading of the cycle of the waveform in response to the frequency selected by the tone frequency selection device without changing the width of the read out waveform to thereby produce a continuous train of time sequential said window functions having a frequency inversely proportional to the period of dead time between the commencement of each successive reading. - View Dependent Claims (16)
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Specification