Noise generator for a polyphonic tone synthesizer
AssigneeKawai Musical Instrument Mfg. Co., Ltd.
InventorRalph Deutsch
Life of this patent
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Abstract
In an electronic musical instrument apparatus is provided for producing a noise-like signal suitable for a variety of musical effect such as the imitation of percussive musical instruments. A noise master data set is created repetitively and independently of tone generation by computing a Fourier algorithm using random values for the Fourier coefficients. The noise master data set is transferred to a noise tone register whose output is sequentially and repetitively read and converted to an analog noise signal. Formant circuitry is used to vary the noise signal's spectrum in a time variant manner and the frequency of an assigned variable frequency clock can be used to vary the spectral bandwidth of the output noise signal.
Claims11
A musical instrument utilizing a noise-like signal generator comprising;
- a random number generator for creating a sequence of random data values,
- a means for computing a noise master data set responsive to said sequence of random data values during each computation cycle of a sequence of computation cycles,
- a first memory means for writing said noise master data set to be thereafter read out,
- a second memory means for writing input data to be thereafter read out,
- means for reading said noise master data set from first memory means and for writing said noise master data set in said second memory means,
- means for repetitiously and sequentially reading out data stored in said second memory means,
- absolute value means for generating the absolute values of data read out from said second memory means, and
- means for converting wherein said generated absolute values of data are converted to provide said noise-like signal.
A musical instrument utilizing a noise-like signal generator comprising;
- a keyboard comprising a plurality of key switches,
- a plurality of tone switches wherein each setting of said tone switches corresponds to a selection of a predetermined sound waveshape,
- a noise signal generation switch,
- digital computing means responsive to setting of said tone and noise signal generation switches for generating a master data set having words corresponding to a succession of points on said selected sound waveshape and for generating a noise master data set comprising words having random values,
- a plurality of registers,
- a noise signal assignor responsive to said noise signal generator switch whereby a member of said plurality of registers is assigned as a noise tone generator if said noise signal generator switch is actuated,
- transferring means responsive to the setting of any of said key switches whereby said master data set is transferred from said digital computing means to selected members of said plurality of registers and whereby said noise master data set is transferred to said member of said plurality of registers if said noise generator switch is actuated,
- 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 connected to said plurality of registers,
- first means for repeatedly shifting stored master data set in each member of said plurality of registers not assigned as a noise tone generator serially to said digital-to-analog convertor means in synchronism with said associated clock generator whereby said 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 tone switches, and
- second means for repeatedly shifting stored noise master data set in said assigned noise tone generator in synchronism with said associated clock generator whereby digital-to-analog convertor means generates a noise like signal having a spectral width determined by a selected key on said keyboard.
Dependencies are inferred from the claim text.