Cracking the unisons

[Ric Brekne]

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For anyone wondering what DSP means, it stands for Digital Signal 
processing and can be used at present (as far as I understand) to 
usefully find only single frequencies at a time. Please see the 
following article.

http://www.cs.hmc.edu/~kperdue/MusicalDSP.html

 Essentially one needs to examine the total wave form of a tone closely 
enough so as to be able to establish its period. Which of course only 
yeilds the fundemental. In order to find multiple frequencies of complex 
tones like the sound of a piano, a FFT is needed. So if the ETD's that 
are out there today do not use FFT's in calculation of the partials 
ladders or for measuring coincidence of any but the fundemental with the 
target frequency... I'd be very interested in seeing how.  

Cheers
RicB


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 > No they donīt and there are good physical reasons why they donīt. (You
 > will find not one tuner at Steinway (at least in Hamburg) who is allowed
 > to service concerts with an ETD for example). This has nothing to do
 > with traditionalism or ignorance to modern technology.
 > Most modern ETDīs are doing fast fourier transformation (FFT) for pitch
 > calculation.

Oh, really? The only one I know of using FFT for anything is
Tunelab, for the spectrum display (and perhaps unison
determination). Pitch matching is done with an entirely different
algorithm. I've put in a fair amount of time writing code and
exploring DSP pitch detection methods, and real world pitch
detection is tough. A pure tone can be measured accurately with an
FFT phase angle, but if there is a way to measure a piano tone
partial accurately in real time (or at all, for that matter) with
FFT, I'd sure like to know the method.

Ron N/

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