1/2 cent difference on unison

[Jim Coleman, Sr.]

Hi Don:

For just a minor correction due to further research. This phenomenon of 
the complete 3 string unison giving off a pitch lower than any of the 3
single strings individually is primarily observable in the 5th and 6th 
octave only. 

I have measured cases
where the difference is as much as .9 cents. Then there are cases where the
difference is negligible even in that area. I don't think anyone yet has a
firm explanation for it. My guess is that it has something to do with the
connection of the strings to the bridge. The bridge may be controlling the
strings to a certain degree. I am hoping that others will begin taking
measurements of this. Perhaps Dr. Sanderson will be able to give us more
insight on this when they finish the development and initial production of
their new SAT III. In the meantime, it is probably safe to adjust the width
of the octaves in that area just a little sharper. Virgil Smith is the one
to be credited with first discovering this phenomenon. I opposed him 
valiantly until my own research proved me wrong.

Jim Coleman, Sr.

On Thu, 29 Jan 1998, Don wrote:

> Hi Bill,
> 
> This is very interesting!
> 
> >  It has been well demonstrated that a
> >properly tuned unison will read about 1/2 cent flat of a single string.  This
> >presents a problem both in aural and electronic tuning.
> 
> Who has demonstrated this and how? There has been some discussion of this
> before on the list. But only Jim Coleman has *posted* his results. I had
> hoped that another technician would try to duplicate his results!
> Regards,
> Don Rose, B.Mus., A.M.U.S., A.MUS., R.M.T., R.P.T.
> "Tuner for the Centre of the Arts"
> drose@dlcwest.com
> 3004 Grant Rd.
> REGINA, SK
> S4S 5G7
> 306-352-3620 or 1-888-29t-uner
>