[sdiy] vocoder filters

bbob fluxmonk at gmail.com
Sun Sep 1 17:05:35 CEST 2019

speaking of back in the day... don't forget Jim Patchell's vocal filter (
http://www.noniandjim.com/Jim/synthmodules/vocalfilter.html).  check out
the picture of the PCB - to me it is an inspiration and a thing of beauty,
but it explains why some folks might want to do it in software!  really
should build mine someday...


On Sat, Aug 31, 2019 at 10:25 PM Bernard Arthur Hutchins, Jr <
bah13 at cornell.edu> wrote:

> Of courses vocoders have “dynamic poles” (not fixed resonances) – else
> what is the point?  In the original application (Voice-Coder) the idea
> was to exploit the redundancy in human speech (10:1 to 50:1 - - said
> redundancy being the repetition of many very similar “cycles” in time that
> constitute a particular vowel/phoneme/syllable). Instead as few as three
> bandpass resonances might well represent a “frame” of 1/5 a second.  A
> loss of quality of stored/transmitted speech for a vast reduction of memory
> required (expensive in the early days). But clearly the resonant
> frequencies changed with each new frame encoded.
> If applied to music, probably one thinks of synthesizing singing or some
> DESIRABLE vocal effect.  I tried this:
> http://electronotes.netfirms.com/AES4.PDF
> The “animator” worked through a series of (LFO controlled – see Fig. 7) of
> POSSIBLE formant frequencies (phonemes both used and unused in a particular
> language).  It worked - it sounded human!  BUT basically like a human
> suffering from food poisoning!   Lesson learned.
> -Bernie
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