Unison coupling

[Kent Swafford]

So in the killer area, short sustain and noticable discrepancy in pitch 
between a single string/whole unison are two manifestations of the same 
problem? Fascinating!

Kent


Ron Nossaman wrote:
>>The frequency of vibrating piano strings is not stable, but tends to 
>>lower as the string continues to sound.
>
>* Excursion amplitude while the string is sounding stretches it sharp. The
>greater the amplitude the higher the attack pitch for any given diameter,
>length, pitch?
>
>
>> In other words, the flatness observed when 
>>strings sound together may just be because the strings get to the flat 
>>part of the envelope faster, fast enough that the sharper part of the 
>>envelope goes by fast enough that it can be missed.
>
>* This sounds real plausible to me. More on a possible "why" further down.

> I agree that this
>probably happens throughout the piano, but why is it most obvious in the
>killer octave area? I think it's because the soundboard impedance is
>usually too low in that area (compressing the envelope by allowing too high
>an energy transfer rate back and forth between strings and soundboard
>assembly), and there are usually plenty of tuned duplexes and short
>backscales in that area bleeding energy from the speaking lengths and
>further compressing the attack phase of the envelope. It probably happens
>just as much in the upper treble, but there usually isn't a discernable
>attack phase in a "dink", so no one much notices. In the lowest bichords,
>The envelope is expanded so much that it's hard to tell if the phenomenon
>exists.