pitch2volt pat.

John Simonton honcho at paia.com
Wed Jan 21 04:12:09 CET 1998


At 02:42 PM 1/20/98 +0100, you wrote:
>For those who are interested:
>
>I just found 3 patents about pitch to voltage conversion:
>

It's not at all difficult to patent them ;-)

Some instruments are easier than others. Percussion (Guitar, Piano) are
hard because they are the ones most likely to have missing fundamental
_and_ complex (chaotic) phase shifts among the harmonics that are present.
Most wind and reed instruments - or anything that sustains - are pretty
easy because of "constant" phase relationships (or at least constant
change) and they rarely have missing fundamentals. Horns are not too hard
on sustained notes, but are difficult to capture quickly because the
characteristic fast attack, fast release, and fast attack again (the "horn
pip") makes them essentially percussive for the first few dozen milliseconds.

Flute and saxophone are very easy. A low-pass filter front-end and
zero-crossing detector are completely adequate for pitch extraction.  But a
low-pass filter, whether frequency or time domain, to extract fundamental
isn't much help if you can't count on the fundamental being there in the
first place. This is not some esoteric effect that a psych dude found was
"significant" by running an ANOVA on the data, it happens in real
instruments and has the practical effect of making a pitch-to-something
converter that will work on all instruments a very difficult problem. You
just about have to have a brain to do it, maybe you could pharm them from
cow's eggs ;-)

-John

---------------------------------------------------------
John Simonton                  PAiA Electronics, Inc
3200 Teakwood Ln.              honcho at paia.com
Edmond OK 73013                http://www.paia.com
405-340-6300                   fax 405-340-6378



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