US4231278A
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Adaptive computation in a digital tone synthesizer
Assignee: Kawai Musical Instruments Manufacturing Co Ltd
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Filing: 1979-04-25
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Granted: 1980-11-04
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Expires: 1999-04-25
Abstract
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 adaptively computing the set of data points in response to values of preselected harmonic coefficients. The computation apparatus advances past all harmonic coefficients of smaller magnitude than a selected threshold thereby reducing the computation time and making the instrument capable of responding to time varying tonal changes.
Inventors
- 👤 Ralph Deutsch
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 16:54
CPC Classifications
G; G10; G10H; G10H7/00; G10H7/08; G10H7/10; G10H7/105
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
221 words
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 points defining the waveform of one cycle of an audio signal are computed by a Fourier transform using stored values of harmonic coefficients and in which the waveform points are transferred sequentially from a note register to a digital-to-analog converter at a rate proportional to the pitch of the tone being generated the improvement for generating said data words in a time interval whose length is determined by the values of the harmonic coefficients comprising: a harmonic coefficient memory means for storing values of harmonic coefficients, memory addressing means for reading out harmonic coefficients from said harmonic coefficient memory, a computation means using said values of harmonic coefficients wherein said data words are computed during a computation cycle, a comparator means whereby a comparison signal is generated in response to a preselected value of a harmonic coefficient read out of said harmonic coefficient memory, and termination means responsive to said comparison signal whereby said harmonic coefficients are inhibited and not provided to said computation means and whereby said computation cycle is terminated thereby causing the duration of said computation cycle to be altered in response to said preselected value of a harmonic coefficient.
Claim 2
Dependent Claim
221 words
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 points defining the waveform of one cycle of an audio signal are computed by a Fourier transform using stored values of harmonic coefficients and in which the waveform points are transferred sequentially from a note register to a digital-to-analog converter at a rate proportional to the pitch of the tone being generated the improvement for generating said data words in a time interval whose length is determined by the values of the harmonic coefficients comprising: a harmonic coefficient memory means for storing values of harmonic coefficients, memory addressing means for reading out harmonic coefficients from said harmonic coefficient memory, a computation means using said values of harmonic coefficients wherein said data words are computed during a computation cycle, a comparator means whereby a comparison signal is generated in response to a preselected value of a harmonic coefficient read out of said harmonic coefficient memory, and termination means responsive to said comparison signal whereby said harmonic coefficients are inhibited and not provided to said computation means and whereby said computation cycle is terminated thereby causing the duration of said computation cycle to be altered in response to said preselected value of a harmonic coefficient.
Claim 3
Dependent Claim
156 words
A musical instrument according to claim 1 wherein said computation means comprises: a word counter incremented at each computation time in said computation cycle wherein said word counter counts modulo the number of said data words; modulo reset whereby a reset signal is created when an increment to said word counter returns the count to an initial state, a harmonic counter incremented by said reset signal wherein the harmonic counter counts modulo a preselected number, an adder-accumulator for adding successive values of the content of said harmonic counter, a sinusoid table comprising a memory storing values of trigonometric functions, a second addressing means for addressing values from said sinusoid table in response to contents of said adder-accumulator, a multiplier means for multiplying each said addressed value from said sinusoid table with a corresponding harmonic coefficient read out from said harmonic coefficient memory means, and a data memory means for storing values provided by said multiplier means.
Claim 4
Dependent Claim
110 words
A musical instrument according to claim 2 wherein said computation means comprises; a second modulo reset whereby a termination signal is created when said reset signal increments said harmonic counter causing it to return to its initial state, clock means for generating timing signals, a counting gate interposed between said clock means and said word counter whereby said timing signals are transferred in response to a control signal, control signal generating circuitry whereby said control signal is created at the start of said computation cycle and whereby said control signal generation is terminated in response to said termination signal created by said second modulo reset thereby terminating said computation cycle.
Claim 5
Dependent Claim
61 words
A musical instrument according to claim 1 wherein said comparator means comprises; a reference signal generation means for creatng a reference signal, and comparison circuitry means responsive to said reference signal and to harmonic coefficients read out of said harmonic coefficient memory wherein said comparison signal is generated if the harmonic coefficient is less than the value of the reference signal.
Claim 6
Dependent Claim
17 words
A musical instrument according to claim 4 wherein said reference signal is generated with time variant values.
Claim 7
Dependent Claim
149 words
A digital polyphonic tone synthesizer in which musical waveshapes are computed by means of a Fourier transform, wherein the computation is adaptive to the values of the harmonic coefficients used in said transform, comprising; a keyboard comprising a plurality of key switches, a plurality of tone switches wherein each setting of the tone switches corresponds to a selection of a predetermined sound waveshape, a plurality of memories containing values of harmonic coefficients, selection means responsive to setting of said tone switches for sequentially selecting harmonic coefficients from said plurality of memories, a reference signal generation means, a comparison means whereby a comparison signal is created when one of said sequentially selected harmonic coefficients is less than said reference signal, and digital computing means responsive to said harmonic coefficients and said comparison signal for generating a master data set comprising points on said musical waveshape according to said Fourier transform.
Claim 8
Dependent Claim
149 words
A digital polyphonic tone synthesizer in which musical waveshapes are computed by means of a Fourier transform, wherein the computation is adaptive to the values of the harmonic coefficients used in said transform, comprising; a keyboard comprising a plurality of key switches, a plurality of tone switches wherein each setting of the tone switches corresponds to a selection of a predetermined sound waveshape, a plurality of memories containing values of harmonic coefficients, selection means responsive to setting of said tone switches for sequentially selecting harmonic coefficients from said plurality of memories, a reference signal generation means, a comparison means whereby a comparison signal is created when one of said sequentially selected harmonic coefficients is less than said reference signal, and digital computing means responsive to said harmonic coefficients and said comparison signal for generating a master data set comprising points on said musical waveshape according to said Fourier transform.
Claim 9
Dependent Claim
61 words
A musical instrument according to claim 6 wherein said digital computing means further comprises; inhibit circuitry interposed between said plurality of memories and said digital computing means wherein in response to said comparison signals said harmonic coefficients are not provided to said digital computing means, and advance circuitry wherein said Fourier transform is not computed in response to said comparison signal.
Claim 10
Dependent Claim
175 words
A musical instrument according to claim 7 further comprising; a plurality of registers, transfer means responsive to the setting of said key switches whereby said master data set is transferred from said digital computing means to selected members of said plurality of registers, a plurality of variable frequency clock generators each associated with a member of said plurality of registers whereby associated registers are shifted at a selected clock rate, means responsive to operation of any member of said plurality of key switches for setting the frequencies of said clock generators to predetermined values assigned to key switches, digital-to-analog converter means coupled to said plurality of said registers, and means for repeatedly shifting the stored master data set in each member of said plurality of registers serially to said digital-to-analog converter means in synchronism with said associated clock generator, whereby the digital-to-analog converter means generates a plurality of analog output signals each having a fundamental frequency determined by a selected key on said keyboard and a waveshape determined by the setting of said stop switches.
Claim 11
Dependent Claim
89 words
A musical instrument according to claim 6 wherein said digital computing means further comprises; a sinusoid table storing sine values, and means for computing numbers Z N in said master data set in accordance with the relation ##EQU2## here q=1,2,3, . . . ,M, N=1,2, . . . ,2M and M is the number of harmonic components defining said number Z N , c q is an element of the harmonic coefficient stored in said plurality of memories and sin π(Nq/M) is a value addressed from said sinusoid table.
Claim 12
Dependent Claim
56 words
A musical instrument according to claim 9 wherein said means for computing numbers computes 2M terms for each value of said number q if said comparison signal is not created and wherein the means for computing numbers does not compute any terms for a value of said c q for which said comparison signal is created.
Claim 13
Dependent Claim
24 words
A musical instrument according to claim 10 wherein said digital computing means is inhibited when all said values of Z N have been computed.
Claim 14
Dependent Claim
32 words
A musical instrument according to claim 3 wherein said comparator means further comprises word reset circuitry whereby said word counter is returned to its initial state in response to said comparison signal.
References Cited (Backward Citations)
US4085644A
Cited
USPTO Annuity & Maintenance Windows
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| 3.5 Years (Year 4) | 1983-11-04 | 1984-05-05 | 1984-11-04 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1987-11-04 | 1988-05-05 | 1988-11-04 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1991-11-04 | 1992-05-05 | 1992-11-04 | $7700.00 | Window Closed / Lapsed |