[CAUT] Re. Link to Young Paper

[Fred Sturm]

On 1/19/07 3:29 PM, "David Brown" <David.C.Brown.2 at asu.edu> wrote:

> Dear Fred-
> 
> I wonder if you could expand on this a bit more. I attempted to calculate FAC
> this way after reading your post but I must have done something wrong. The
> difference between the first and fourth partial of A4 seemed to yield a wider
> octave ( larger A number, to be expected I suppose) than the normal reading,
> but the difference between the first and fourth partial of C 6 yielded numbers
> well into the 20¹s or 30¹s! I tried the the difference between the first and
> second partial of C7 as well and still no real usable numbers for me. There
> must be a way to enlighten me!
> 
> 
> Hope all is well in New Mexico.
> 
> Regards-
> 
> David

Hi David,
    The A4/A6 difference needs to be multiplied by 0.8, to factor out the
difference between 1st and 2nd partial and leave the difference between 2nd
and 4th partial. The C6/C8 difference needs to be multiplied by 0.2 to
factor out the difference between 2nd and 4th partial and leave the
difference between 1st and 2nd partial. The difference between 1st and
second partial is 1/4 the difference between 2nd and 4th partial (it¹s a
logarithmic scale, based on a square of the difference between partial
numbers, kind of).
    So, if you read A4/A6 as 10 (zero A4 and read its 4th partial at A6 as
plus 10 cents), you enter 8 as the A number. When you have calculated the
tuning, the number for A4 (the tuning offset, tuning it¹s 4th partial) will
be 10. For C6/C8, if the number is 35 (C6 zeroed, its 4th partial at C8 read
as plus 35 cents), you enter 7. (Obviously when you enter the number, you
have to go to the right note name and octave, and scroll cents up or down).
    Is this clearer?
    (BTW, David is referring, I believe, to some posts I sent to pianotech
around ten years ago, when I was coming to terms with my SAT).

Regards,
Fred Sturm
University of New Mexico

 
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