[pianotech] inharmonicity in piano wire

[paul bruesch]

I generally tune with a SAT-3. In order to calibrate it to the piano (as I
occasionally refer to it for a curious customer) one must first tune F3, A4,
and C6 to zero deviation from (theoretical) partials at F5, A5, and C6
respectively. One then measures the inharmonicity differences between that
partial and an octave above... i.e. F6, A7, C7.  (SAT users refer to this as
FAC.)

After doing a pitch correction, I always re-measure FAC for my fine tuning,
and it is *always* different. Sometimes it's quite significantly different,
and I have always wondered why, since the center strings of F3, A4, and C6
are at the same tensions for both the pre-pitch-correction reading and the
pre-fine-tuning reading.

And how does keeping a piano at a particular pitch result in lowering
inharmonicity?

Paul Bruesch
Stillwater, MN

On Thu, Feb 12, 2009 at 12:49 PM, Don <pianotuna at accesscomm.ca> wrote:
<snip>

> Over time, if a piano is kept at a
> particular pitch, inharmonicity may often become lower too--so it is best
> to remeasure at every service call. YMMV

</snip>
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