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Subject:Pitch shift
Posted by: sergiob
Date:1/24/2002 11:43:39 AM

I'm using Sound Forge 5.
I'm trying to setup a clarinet soundfont from scratch and would like to do pitch shift on some of the samples. For example, I have an A4 sample that the spectrum analysis gives ma 446Hz. How do I change the pitch to get a perfect 440? I've tried using the Pitch Shift (using Cents shift), but it is a PITA cause I have to do a trail-and-error routine going back and forth between Pitch Shift and Spectrum Analysis.
Is there a better way?
Thanks,
Serge

Subject:RE: Pitch shift
Reply by: Rednroll
Date:1/24/2002 12:06:29 PM

Antares Autotune plugin, would probably be the easiest to do this, otherwise you probably have to figure out how many CENTS to pitch your frequency down using pitch change. I'm sure there's a mathematical relationship to Cents vs. Frequency.

Subject:RE: Pitch shift
Reply by: Chienworks
Date:1/24/2002 2:24:45 PM

A cent is merely 1% of a semitone, and a semitone is factor of 1.059463.
Therefore a cent is a factor of 1.00057779 (more or less).

To shift from 446Hz to 440Hz requires a factor of 0.986547085. To
convert this to cents, get out your calculator and use:
cents = log (new freq/old freq) / log (cent factor)
cents = log (440/446) / log (1.00057779)
cents = log (0.986547085) / log (1.00057779)
cents = -0.005882182 / 0.000250858
cents = -23.444820366

(I used common log base 10 here, but natural log works as well. Use
whichever key your calculator has, just make sure you use the same key
both times.)

The negative means you'll go down 23 cents. If the result was positive
you would go up 23 cents. Unfortunately Sound Forge only lets you use
whole cents (so ignore my fascination with lots of decimal places!)

While experimenting in Sound Forge using spectral analysis on a 446Hz
sine wave, i noticed it reported 453Hz. Hmmmm. So i'm guessing that
spectral analysis isn't terribly accurate. Let your ear be the final judge. If
the shift doesn't come out quite right, undo and try again. At least this
formula will give you a starting point.

Subject:RE: Pitch shift
Reply by: sergiob
Date:1/26/2002 7:57:07 AM

Thanks

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