Drifting Unisons

Jim Coleman, Sr. pianotoo@IMAP2.ASU.EDU
Mon Nov 8 18:28 MST 1999


Hi Fred:

I believe the arrangement of tuning pins in the "B" probably helps the
unisons stay better because the 3 pins of each unison are closer together.
There may be more variation in the pitch of the neighbor notes due to
the weather changes, but one does not notice changes in temperament as
readily as one notices bad unisons.

Jim Coleman, Sr.

On Sun, 7 Nov 1999, Fred S. Sturm wrote:

> I guess I wasn't clear in what I wrote. Steinway B's definitely exhibit 
> the unison drift phenomenon, and to a pretty marked degree. What I was 
> trying to point out was that Steinway B's also have a unique tuning pin 
> pattern (well, maybe there are similar ones, but none comes to mind), 
> where there is an immense difference in "waste length" on the tuning pin 
> side between adjacent unisons. The pins for one unison are set forward, 
> right next to the agraffes, next unison set back toward the stretcher, 
> alternating throughout the treble section of the piano. If the amount of 
> pinblock wood between flange and tuning pin were the major factor in 
> making the right string of a unison move farther in pitch than the left, 
> wouldn't we see a similar difference between all the strings of one 
> unison compared with all the strings of its neighbor? The difference in 
> waste length between the left string of C4 and the left string of C#4 is 
> greater than the difference between the left string of C4 and the right 
> string of C4. 
> 	
> Fred
> 
> Newton Hunt wrote:
> > 
> > When the humidity goes from 15 to 85 percent every year for 10 years
> > the pattern becomes quite obvious even on Bs but, as you say, less so
> > mostly because the block in so well integrated into the case it's
> > movement is restricted.  Small pianos in the S&S line show more of the
> > pattern.
> > 
> > Se, essentially, I beg to differ.
> > 
> >                 Newton
> > 
> > >
> > > That might be an adequate explanation except for the fact that Steinway
> > > model B grands don't show a big difference, if any, between adjacent
> > > unisons where the tuning pin pattern is offset (bigger difference in
> > > distance from agraffe to pin from unison to unison than between pins in
> > > one unison). Also, upright pianos show the same tendency (right tuning
> > > pin shows more movement), and the distances are reversed from that of
> > > grands (right pin closest on upright, farthest on grand).
> > >
> > > Regards,
> > > Fred S. Sturm, RPT
> > > University of New Mexico
> 


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