[78-L] World 1920s Records

[Jeff Lichtman]

>Does anyone know the cordinnates formular to play the variable speed 1920s
>World and Vocalion record recordings at the correct speed on the computer? I
>would like to transfere some of the dance band tracks to CD. I've played
>around with Adobe and Soundofrge with no luck so far.
>
>Jamie

I don't know what you mean by "co-ordinates formula." Sound Forge has 
a pitch shifting tool (under the Effects menu select "Pitch" followed 
by the "Shift" sub-menu). You can set the number of cents by which to 
adjust the pitch - one cent is a hundredth of a semi-tone, or one 
twelve-hundredth of an octave.

There's a simple formula to convert a frequency ratio to cents. 
Suppose you have a signal of 430 Hz, and you want to speed up the 
recording to where the signal is 440 Hz (concert A). The formula is:

cents = 1200 *  (log(desired frequency / current frequency) / log(2))

In this case, it would be:

cents = 1200 * (log(440 / 430) / log(2))

The base of the logarithm doesn't matter as long as it's the same in 
both the numerator and denominator. Using the natural log, we get:

cents = 1200 * (0.022989518224698739423565307535635 / 
0.69314718055994530941723212145818)

cents = 1200 * 0.033166863935199317315221406257726

cents = 39.800236722239180778265687509271

Rounding to one place after the decimal point, we see that we need to 
speed up the recording by 39.8 cents.


                        -        Jeff Lichtman
                                 jeff at swazoo.com
                                 Check out Swazoo Koolak's Web Jukebox at
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