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From: mhorne@ka7axd.wv.tek.com (Michael T. Horne)
Newsgroups: comp.dsp
Subject: Re: Adjust-Speed CD player?
Message-ID: <4671@orca.WV.TEK.COM>
Date: 25 Sep 89 05:35:52 GMT
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Organization: Tektronix, Inc., Wilsonville, OR
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In a recent article by d88-jwa@nada.kth.se (Jon W{tte):
>>frequency scaling algorithm, perhaps by doing a digital mix with a reference
>>(digital) carrier (i.e. ref = 100 Hz for a 100 Hz shift upward in frequency),
>>followed by a carrier and lower sideband suppression...
>
>As I've said before: that's not scaling, that's OFFSET ! You can't do that
>to MUSIC, because music has a realative overtone spectra.

Ah.  Having arrived at this discussion in mid stream (without the benefit of
context), I believe that the question is about scaling an arbitrary `musical'
(from the viewpoint of the average person) sequence up or down in frequency
while retaining the `musical-ness' of it. :)  I still stand by my suggestion
of shifting an arbitrary spectrum up/down in frequency by doing a digital
mix, however, I agree that it will not generate the desired effect for use
in scaling music.  It would appear that the `vocoder' method may provide
arbitrary control (e.g. true (multiplicative) scaling) for generating such
desired effects.

>And imagine the effect this has on complex waveforms like a violin or a
>piano...

Could you please elaborate on the typical spectra of a given note on a
piano or violin?

Mike

Michael T. Horne                                      VSG/ITD, Tektronix, Inc.
mhorne@ka7axd.wv.tek.com                                        (503) 685-2077