<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html> <head> <meta content="text/html;charset=ISO-8859-1" http-equiv="Content-Type"> </head> <body bgcolor="#ffffff" text="#000000"> 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. <a class="moz-txt-link-freetext" href="http://www.cs.hmc.edu/~kperdue/MusicalDSP.html">http://www.cs.hmc.edu/~kperdue/MusicalDSP.html</a>  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 -------------------------------- > No they don´t and there are good physical reasons why they don´t. (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 ETD´s 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 </body> </html>