Killer Octave & Pitch Raise

[Terry]

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When I raise the pitch of a piano, typically I find that I need to pull =
an area of the treble, commonly around the sixth octave or so, a bit =
extra so that area does not end up flat when the pitch raise is =
completed. I use typical pitch raise overpulls - 20% in bass, 25% in =
tenor and 33% or so in treble - but that one octave or so in the treble =
needs to go a little further - maybe 35 or 38%. I find this to be true =
on most pianos.

My understanding is that one factor that may conspire to produce a =
killer octave (low volume and/or short sustain) in a piano is the fact =
that the killer octave area is also the area the long bridge is curved =
most - rather than having the downbearing supported in part by a =
straight (or nearly so) bridge (like in the tenor), the curved part of =
the long bridge in the killer octave area is more prone to rolling - I =
know, not rolling - actually soundboard deformation - but I'm trying to =
point out that it can rotate in this area more easily than other areas.

My question is - might these two phenomena be related? Is the killer =
octave area more prone to going flat because the bridge is rotating (I =
suppose in part due to soundboard not having enough support in that =
area)?

Thanks for any thoughts.

Terry Farrell
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