Polyphonic tone synthesizer

A musical instrument comprising;

• a first memory means for writing master data set to be thereafter read out, wherein number N designates the address of words in said first memory means,
• means to set contents of first memory means to zero values at start of computation cycle,
• first means for computing numbers Z(N) in master data set in accordance with the relation ##EQU4## where q=1,2,3, . . . W, N=1,2, . . . , W and W is the number of harmonic components defining said number Z(N) in said master data set, and c.sub.q is the harmonic coefficient of the corresponding q.sup.th harmonic component, said first means comprising;
• a memory storing said harmonic coefficients c.sub.q,
• a sinusoid table comprising a memory storing values of sin(.pi..phi./W) for 0.ltoreq..phi..ltoreq.2W at intervals of D where D is a resolution constant,
• harmonic component evaluation circuitry utilizing said memory and said sinusoid table to calculate c.sub.q sin(.pi.Nq/W) for each of the W harmonic components in accordance with a selected value of N,
• means for successively algebraically summing output c.sub.q sin(.pi.Nq/W) of said harmonic component evaluation circuitry with values of word N written in first memory means,
• second memory means for storing a master data set to be thereafter read out,
• second means responsive to first means for transferring said master data set from first memory means to second memory means,
• means for converting a master data set to a musical waveshape, and
• third means responsive to said second means for repetitively reading out the words of said master data set from second memory means and providing said read out words to said means for converting.

A musical instrument comprising;

• a first memory means for writing master data set to be thereafter read out, wherein number N designates address of words in said first memory means,
• means to set contents of first memory means to zero values at start of computation cycle,
• first means for computing numbers y(N) in said master data set in accordance with the relation for a discrete generalized Fourier transform ##EQU5## where q=1,2, . . . ,M, N=1,2, . . . ,M and M is the number of a generalized harmonic coefficient of the corresponding generalized q.sup.th component, said first means comprising
• a harmonic memory means storing said generalized coefficients a.sub.q,
• a function table comprising a memory storing values of orthogonal function .phi..sub.q (ND), where D is a resolution constant
• generalized harmonic component evaluation circuitry utilizing said harmonic memory means and said function table to calculate a.sub.q .phi..sub.q (N) for each of the M generalized harmonic components in accordance with a selected value of N,
• a means for successively algebraically summing output of said generalized harmonic component evaluation circuitry with contents of word N in first memory means,
• second memory means for storing a master data set to be thereafter read out,
• second means responsive to first means for transferring said master data set from first memory means to second memory means,
• means for converting a master data set to a musical waveshape, and
• third means responsive to said second means for repetitively reading out the words of said master data set from second memory means and providing said read out words to said means for converting.

A musical instrument comprising;

• means for computing during a computation cycle a master data set corresponding to the values of a series of points defining a musical waveform,
• first memory means for storing said master data set generated by said means for computing,
• second memory means for storing input information to be thereafter read out,
• means for transferring the data set from said first memory means to said second memory means during a transfer cycle,
• means for repetitiously reading out the data set from said second memory means at any selected one of a plurality of different rates, and
• means for producing musical sound from said data set read out from said second memory means.

A digital polyphonic tone synthesizer 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,
• digital computing means responsive to setting of said tone switches for generating and storing a master data set having words corresponding to a succession of points on said selected sound waveshape,
• a plurality of registers,
• transferring means responsive to the setting of any 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 convertor means coupled to said plurality of registers, and
• means for repeatedly shifting stored master data set in each member of said plurality of registers serially to said digital-to-analog convertor means in synchronism with said associated clock generator, whereby digital-to-analog convertor 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.