Inharmonicity

[A440A@aol.com]

>m time to time I read about inharmonicity of piano strings on this 
>list.  I would be grateful if someone would clarify for me exactly what 
>inharmonicity is and how it affects piano tuning.     

   Greetings, 
Inharmonicity is, literally, the lack of harmonicity.  In the tuning venue, it
refers to the fact that partials produced by piano wire are not exact interger
multiples of the fundamental frequency, but rather, are higher values. 
    An ideal string, with no inharmonicity, tuned to 100 Hz  would produce its
second partial at 200 Hz.  However, a real string will exhibit a second
partial of 200 + something. This is inharmonicity.  
   When tuning an octave, by attempting to match the fundamental of the upper
note to the second partial of the lower note,  the upper notes fundamental
will be slightly more than double the Hz of the lower fundamental, since the
lower note's partial is increased due to the inharmonicity.  
Hope this helps. 
Ed Foote