[pianotech] Stretch in tuning

[tlneely]

Hi all, 
As we all know, when tuning up and down from the temperament, octaves are 
stretched from the theoretical pitch of pure octaves as one might find
on a pipe organ due to the piano being an inharmonic instrument. We 
determine this expansion based upon test intervals and "let the piano
tell us" how much it should be.

For years at conferences I have heard respected folks discuss that 
you have to "stretch the octaves". Everyone nods their heads wisely, 
and the discussion moves on.

My question is this- Is the stretch being discussed in addition to 
that indicated by the tests? Should one do this. If so why and how much?

I suppose I should confess here that I learned to tune aurally on harpsichords
and fortepianos where the inharmonicity is much less than in the piano (using 
equal beating historical temperaments). I use an ETD for piano work(have owned 
most all of them over the years).

Thanks, 
Terry Neely