Kimball International, Inc.

Purdue Research Foundation

Steven C Bass

Joseph P Fitch

Neal C Gallagher

Edward J Coyle

Thomas W Goeddel

Ronald G Harber

A method and apparatus of digitally filtering an M-level signal decomposes the M-level signal into M-1 binary threshold signals by thresholding it at each value from 1 to M-1. The kth threshold signal has the value 1 at a given position if and only if the input signal is at least k at that position; otherwise it has the value 0. Filtering each of the M

Digital filtering by threshold decomposition

A tone generation system intended primarily for use in electronic musical instruments wherein a digital representation of a harmonically rich waveform is sampled, and a musical tone is produced therefrom. The stored waveform could be the four term Blackman-Harris window function, which has negligible side lobes and thus greatly attenuated higher harmonics. The stored function is read out at a fixed rate, but the time periods between successive readings of the waveform are varied to thereby vary the frequency of the output signal.

Digital tone generation system utilizing fixed duration time functions

An electronic musical instrument wherein purely digital techniques are utilized for generating the basic waveform train and also keying the waveform train so as to have the customary keying envelope with attack, sustain and decay portions. The wavetrain is a cyclically repeated series of four-term Blackman-Harris window functions, wherein there are preferably eight such functions in each series. A plurality of individual keying envelopes are generated by a piecewise linear technique, and these envelopes are assigned respectively to the waveforms in the series so that the relative amplitudes of the waveforms can change with time over the life of the tone. This results in modulating with time the harmonic content of the tone.

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Stockwell, IN, United States of America

Steven C Bass