Ensemble and anharmonic generation in a polyphonic tone synthesizer

Abstract

A musical ensemble effect results when two tones slightly out-of-tune with respect to each other are sounded together upon selection of a single instrument key. Herein, apparatus is disclosed for producing an ensemble effect in a polyphonic tone synthesizer of the type wherein musical notes are produced polyphonically by computing a master data set, transferring data set to buffer memories, and repetitively converting in real time contents of memories to notes. A multiplicity of master data sets are created repetitively and independently of tone generation by computing a generalized Fourier algorithm using stored sets of generalized Fourier coefficients. The phase of such master data sets are generated with time varying phase shifts to provide theout-of-tune ensemble effects. The phase shifted master data sets are combined and transferred to buffer memories from which such data is converted to musical sounds. Means are included for inhibiting phase shifts of fundamental frequency components and thereby creating musical tones having anharmonic overtones.