Unified tone generation in a polyphonic tone synthesizer
AssigneeKawai Musical Instruments Mfg. Co., Ltd.
InventorRalph Deutsch
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Abstract
In a musical instrument having one or more tone generators in which a plurality of data words corresponding to amplitudes of a corresponding number of evenly spaced points defining the waveform of an audio signal composed of a number of unified tones are generated by the combination of three master data sets. The three master data sets are computed separately from stored sets of even and odd harmonic coefficient values. The master data set values are combined using their symmetric properties and are transferred sequentially to a digital-to-analog converter in repetitive cycles at a rate proportional to the unison pitch of the corresponding keyboard note to produce the tone color of a combination of unified tones.
Claims18
In a musical instrument in which successive points of a musical waveshape are computed by means of a discrete Fourier transform using a set of harmonic coefficients stored in numerical order corresponding to the harmonic number of the Fourier transform to form a master data set, apparatus for simultaneously producing a plurality of unified tones at pitches responsive to the setting of a plurality of stop switches comprising;
- a means for computing a plurality of master data sets during each of a plurality of computation cycle segments of a sequence of computation cycles wherein a first master data set is computed using the complete stored set of said harmonic coefficients, wherein a second master data set having odd symmetry is computed using the even numbered harmonic coefficients selected from said set of harmonic coefficients, and wherein a third master data set having even symmetry is computed using the odd numbered harmonic coefficients selected from said set of harmonic coefficients,
- a first memory means comprising a plurality of master memory means for storing said plurality of master data sets,
- a second memory means comprising a plurality of note memory means for storing input data to be thereafter read out,
- data transfer means for addressing master data sets out from said plurality of master memory means and for storing said addressed master data sets in said plurality of note memory means in said second memory means,
- a means for producing musical waveshapes from master data sets read out of said plurality of note memory means,
- a variable frequency clock generator, and
- data reconstruction means responsive to said variable frequency clock generator whereby master data sets are read out of said plurality of note memory means in said second memory means and are combined to form a combined data set using combination circuitry responsive to the even symmetry of said third master data set and the odd symmetry of said second master data set and whereby the combined data set is furnished to said means for producing musical waveshapes thereby creating said plurality of unified tones.
In a musical instrument having one or more tone generators in which successive points of a musical waveshape are computed by means of a discrete Fourier transform, apparatus for producing unified tones at selectable pitches comprising;
- a keyboard comprising a plurality of key switches,
- a plurality of stop switches for selecting the pitches of said unified tones,
- digital computing means responsive to the setting of said stop switches for generating a main master data set, an even main master data set and an odd main master data set,
- a plurality of memory means wherein each memory means comprises three data registers,
- transfer means responsive to the actuation of said key switches wherein said main master data set, said even master data set and said odd master data set are transferred from said digital computing means for selected members of said plurality of memory means,
- a plurality of variable frequency clock generators each associated with a member of said plurality of memory means whereby associated registers are addressed at a selected clock rate,
- means responsive to the actuation of any member of said plurality or key switches for setting the frequencies of said clock generators to predetermined values assigned to said key switches,
- digital-to-analog converter means coupled to said plurality of registers, and
- means for addressing data from said plurality of registers whereby addressed data is combined and furnished to said digital-to-analog converter means thereby generating said unified tones at different pitches.
Dependencies are inferred from the claim text.