Pitch Raises ... Overpull Percentage

[Farrell]

Yikes! You must have raised the pitch of one or two pianos! What a perfectly complete and accurate explanation!

Except the Verituner. It does not use any averaging for past notes. It measures the flatness of each note and directly calculates the user-designated overpull for that note based only on the flatness of that one note. I wish that it was able to incorporate info from other notes. But I do not find that a problem in use. I just mentally massage the indicated overpulls as I go, much like I used to do with my SATs.

Terry Farrell
  
----- Original Message ----- 
From: "Robert Scott" <rscott@wwnet.net>
To: <pianotech@ptg.org>
Sent: Thursday, August 22, 2002 6:57 AM
Subject: Pitch Raises ... Overpull Percentage


> Conrad Hoffsommer asks:
> 
>  >For the benefit of newbies and non-ETD users, could you review just what
>  >that is 20%/25%/30% OF?
>  >I think I know, but I get confused ezee...
> 
> The question is a good one.  Different ETDs apply the 20%/25%/30% to 
> different things.  I think the SAT applies the percentage to the flatness 
> of a single note.  You can periodically measure a new note as you tune so 
> as to update what the percentage applies to, but it is still one 
> note.  TuneLab and the RCT both measure every note before it is 
> tuned.  They use running averages to determine the flatness of the region 
> of the piano where you are tuning, and apply the overpull percentage to 
> that running average.  I think RCT uses what is sometimes called a "boxcar" 
> average, which is an ordinary average of the last few notes.  TuneLab uses 
> a declining weight average to estimate the flatness of the piano where you 
> are tuning.  A weighted average gives more weight to the more recent notes 
> and less and less weight to notes that are more distant from where you are 
> tuning, in order to form the average.  In any case, however it is 
> determined, the overpull percentage is applied to the flatness of the 
> piano, and then the result is added on to the target pitch for the note you 
> are about to tune.  For example, if the measurements say the piano (or the 
> region where you are tuning) is 40 cents flat, and the overpull percentage 
> is 25%, then the ETD will set a target pitch that is 10 cents higher than 
> normal, in anticipation of the pitch falling that 10 cents by the time you 
> finishing tuning the whole piano.
> 
> -Robert Scott
>   Real-Time Specialties
>