Issues with Pitch Raises, Particularly with Two Treble Struts

David Kissam

I have experienced an issue with pianoscope's overpull calculations for the strings between the first and second treble plate struts. So far I have done large pitch raises (over 50 cents overall) on two pianos (a Kawai vertical and a Yamaha grand) with two struts in the treble. For both pianos, the strings between the treble struts were left significantly sharp, maybe 10-15 cents on the Kawai and 5-10 cents on the Yamaha.

Pianoscope's pitch raise has always given me great results in the bass and middle section, and treble turns out good when there is only one plate strut. The high treble (approximately the top octave and a half) has tended to be quite flat (10-20 cents) after large pitch raises. By "large pitch raises", I mean that I'm raising the treble strings by 50-100 cents.

Does anyone else have similar experiences? I'm going to start aiming about 10 cents below pianoscope's target between the treble struts, and perhaps a bit above the target in the high treble.

I am new to tuning, by the way. I have been tuning pianos at a store for the past few weeks, so I don't have much experience at this point.

OldMike

I also have noticed that the treble seems off when I pitch raised my Steinway Vertegrand, which has two treble struts. I thought it was me, but other piano’s I’ve pitch-raised were fine; they had only one treble strut.

Like David I’m also relatively new at tuning.

David Kissam

This week I did a pitch raise on a new Kawai GL-40. It was about 25 cents flat (median value). In between the two treble struts, pianoscope was calling for an overpull of about 10 cents, which was higher than its target for the strings below the lower strut and above the higher one. I aimed instead for around 8 cents, and this worked well. Some strings ended up a few cents flat, and some were a few cents sharp, meaning the overall tension in the section was pretty close to where it needed to be. If I had pulled everything up to pianoscope's target, the whole section would have been sharp on average.

I then tuned a new GL-50 that was about 15 cents flat (median value). When I got to the first treble strut, I set the manual offset in the pitch raise settings to -25%. When I got to the second treble strut, I set the offset back to 0%. This worked very well, and required only small adjustments on a quick second pass.

So that's my method for now: manually set the offset to -25% between the treble struts, if there are two of them. All 4 pianos that I've tuned with 2 treble struts have had this problem with pianoscope.