AbstractA keyboard operated musical instrument is disclosed in which musical tones are created by reading out data values stored in a waveshape memory. The number of stored data points is reduced by storing the data values in segments corresponding to one-half of the number of data points for a period of a waveshape. By using synthesized data having a symmetry about the midpoint, the
second half of the waveshape is recovered by a forward and backward memory address read of each waveshape segment. After reading each segment a predetermined number of cycles, an abrupt jump is made to the next segment of waveshape data points. The fundamental frequency of the tone is varied in a temporal manner by changing the memory advance rate of reading waveshape data out
of memory in response to a frequency offset data corresponding to each segment of the waveshape data. An alternative embodiment is disclosed for a tone generator in which the musical waveshape is computed in real time from stored sets of harmonic coefficients.ClaimsI claim:
1. In combination with a keyboard operated musical instrument having an array of keyswitches, apparatus for producing a
musical tone having temporal variations of a fundamental frequencycomprising;
an assignor means whereby a detect data word is generated in response to each actuated keyswitch in said array of keyswitches and whereby one of a plurality of tone generators is assigned to each actuated keyswitch and whereby a correspondingdetect data word is provided to the corresponding said assigned tone generator; and
said plurality of tone generators each of which comprises,
a waveshape memory means for storing a plurality of data words stored in contiguous segments of data words,
a frequency number generator means wherein a frequency number is generated corresponding to said provided defect data word,
a frequency number scaling means wherein each said generated frequency number is varied in magnitude in response
to a time variant scale signal to produce a scaled frequency number,
a scaling generator means for generating said time variant scale signal,
a memory addressing means responsive to said provided detect data word whereby a selected segment of data words is read out from one of said waveshape waveshape memory means at a memory advance rate responsive to said scaled frequency number andwhereby said selected segment of data words is read for a preselected number of timing periods during each of which the stored data words in said segment of data words is read out in a first order followed by reading out the same segment of data words inreverse order, and
a conversion means for producing a musical tone responsive to data words read out from said waveshape memory means.
2. In a musical instrument according to claim 1 wherein said assignor means comprises assignor circuitry whereby said scaled frequency number is transferred to one of said plurality of tone generators assigned to a corresponding detect dataword.
3. A musical instrument according to claim 2 wherein said memory addressing means comprises;
a
timing clock for providing timing signals,
an adder-accumulator means, comprising an accumulator responsive to said timing signals for successively adding said scaled frequency number to the contents of said accumulator to produce an accumulated frequency number, and
a reading means responsive to said scaled frequency number and responsive to said accumulated frequency number whereby a selected segment of data words is
read out from said waveshape memory means corresponding to said assigned tone generator fora preselected number of timing periods.
4. In a musical instrument according to claim 1 wherein said assignor means comprises;
a keyswitch state detect means wherein a detect signal is generated in response to each actuated keyswitch in said array of keyswitches, and
an encoding means f
