G - Physics – 10 – H
Patent
G - Physics
10
H
84/1.1
G10H 1/00 (2006.01) G10H 7/10 (2006.01)
Patent
CA 1062515
Abstract of the Disclosure In a polyphonic electrical musical instrument, waveforms are synthesised using independant, repetitive computation and data transfer cycles. During the computation cycle a master data set is created by implementing a discrete Fourier algorithm using a stored set of harmonic coefficients which characterize the basic resultant musical tone. The computations are carried out at a fast rate nonsynchronous with any musical frequency. Provision is made for time varying the amplitudes of the computational orthogonal functions so that the musical effect of sliding formant filters is generated. Preferably, the harmonic coefficients and the orthogonal functions are stored in digital form, and the computations are carried out digitally. At the end of the computation cycle a master data set has been created and is temporarily stored in a data register. Following a computation cycle, a loading cycle is initiated which transfers the number data set to a collection of read-write memories. The transfer for each memory is initiated by detection of a synchronizing bit and is timed by a clock which is asynchronous with the main system logic clock and has a freq- uency of Pf, where f is the frequency of a particular note assigned to a memory and P is two times the maximum number of harmonics in the musical waveshape. The transfer cycle is completed when all of the memories have been loaded, at which time a new computation cycle is initiated. Tone generation continues uninterrupted during computation and load cycles. A time shared digital-to- analog converter transforms the output data from the read-write memories to analog voltages assigned to individual tone channels. The digital-to-analog converter is time sequenced with each memory output data conversion to provide attack, decay, sustain, release, and other amplitude modulation effects.
258884
Deutsch Leslie J.
Deutsch Ralph
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