setting pitch with a fork

[Bernhard Stopper]

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Hi Bob,

Thats what i do also first.  (A4-F2, 2 8aves +m3rd)
I proceed then with the sixth F2-D3 to the same beatrate, what is =
resulting in a pure 12th in D3-A4.
Spacing this 12th equally results the P12 tuning.


regards,

Bernhard

  ----- Original Message -----=20
  From: BobDavis88@aol.com=20
  To: pianotech@ptg.org=20
  Sent: Friday, August 20, 2004 8:52 AM
  Subject: Re: setting pitch with a fork


    "I strike the F below the A and listen to the fork A along with the =
F. I count those beats. Then I remove the fork and play the F and the A =
and count those beats. "
  I don't know if the writer really meant literally "the F below the A", =
but I also saw a reference in another post to a "F2-A3" comparison with =
the fork, so I just wanted to make it clear that although F2, F3, and F4 =
will all beat against A4, only the F2 [2 8ves + M3rd] will give an =
accurate comparison between an A4 fork and the A4 note on the piano. =
Here's why:

  The 5th partial of F2 is approximately equal to the fundamental of A4. =
In a tuned piano, it will be about 4 beats flat of both the fork and the =
note, but it can be set anywhere comfortable. I like 5 or 6 beats even =
better. When A4 on the piano is in tune with an A4 fork, the beat of =
either against the F2 beat-producer note will be the same. This is such =
a great method because, even as the notes become in tune, the beats =
remain in a comfortable range [4 to 6/sec] in which the ear is amazingly =
adept at comparison. On the other hand, in trying to match a note =
directly to a fork, the closer the match, the slower the beat. And, it =
never becomes completely clean, because of beating between harmonics of =
the source and "inharmonics" of the piano. Just last Saturday, our =
Chapter set an A as a group by the F2-A4 method, and were very quickly =
able to agree on a setting which we then measured electronically as =
being only 0.2 cents off. That's not bad. By the way, we used an =
AccuFork. We had a grand with a sostenuto, which you can use to hold =
down the F2, but I also demonstrated playing it and jamming a mute =
between it and F# to hold it down, then tuning the A4.

  The 5th partial of ~F3~ on the other hand, is ~A5~, which matches the =
desired A4 at its SECOND partial, A5 [a 5:2 match]. The A5 produced by =
the fork is harmonic, but that produced by the piano is a little sharp. =
Matching this coincidence causes the piano's A4 to be slightly flat. =
F4-A4 [a 5:4 match, coincident at A6] would produce an even flatter A4, =
with equal beats between the fork and piano.

  I hope that's clear. We're probably all on the same page, but I just =
wanted to make sure everyone out there knows why only F2 works =
accurately.

  Bob Davis
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