Octave Tuning

[jason kanter]

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This is the third-tenth test. For example, F3-A3 and F3-A4. The fifth
partial of F3 beats at x/second with the second partial of A4. Then you make
the fifth partial of F3 beat at exactly the same x/second with the fourth
partial of A3. Voila, a perfect 4:2.
  -----Original Message-----
  From: pianotech-bounces@ptg.org [mailto:pianotech-bounces@ptg.org]On
Behalf Of Matthew Todd
  Sent: Wednesday, September 22, 2004 9:54 AM
  To: Pianotech
  Subject: Re: Octave Tuning


  Now, how exactly do you tune the fourth partial of the lower octave note
to the second partial of the upper octave note?  I have heard that some
techs just tune the octave 1/2 a beat wide, and leave it at that.

  Now you can call me stupid

  Matthew

  Don <pianotuna@accesscomm.ca> wrote:
    Hi Mathew,

    Current thought is that a unison is the only "pure" item in tuning. An
    Octave can only be "beat free" at one partial at a time. Do an archive
    search for octaves and you will get loads of hits.

    narrowest possible octave 2:1; a3 to a4 beatless at a4
    wider 4:2; a3 to a4 beatless at a5
    wider 6:3; a3 to a4 beatless at e6

    It is common to tune a3 to a4 somewhere between 4:2 and 6:3--just to
make
    the task a little more difficult. I believe this is what Virgil Smith
does
    when he attempts to tune the "whole sound" of the octave. I.E. his 4:2
    beats at a rate which may "cancel" the beat of the 6:3. How long such a
    "balance" will last is dependant on nothing in the enviroment changing,
    including barometric pressure.

    More on unisons:

    We also have to deal with the "coupled" motion of piano strings. The
bridge
    is a f! lexible termination. Some studies have suggested that a one
hertz
    difference in two strings will result in zero beating heard. One hertz
at
    A4 is approximately 4 cents--a huge number for a unison to be "out".
There
    is also some suggestion that a truely "pure" unison gives the piano a
    rather "dead" sound with poor sustain.

    Inharmonicity:

    There is no doubt that the impedance mismatch between the strings,
bridge
    and soundboard produces a measureable effect on the width of octaves. In
    some cases this "para inharmoncity" can be a negative number.
    Translation--the narrowest octave would be smaller than a "theorectical"
2:1.

    Setting Temperament:

    I'd suggest you use one of the "self correcting" temperments such as the
    Baldassin-Sanderson. Have a look here:

    http://www.accu-tuner.com/SATIIImanual/apf.html

    At 07:42 PM 21/09/2004 -0700, you wrote:
    > need some help from all of you. Is it true that the two things that
    &g! t;remain pure in a piano when we tune is unisons and octaves? And if
we do
    >that, the octave will have a slight beat to it, right? I think I missed
    >something. You guys are great! Thanks!!
    >Matthew
    >__________________________________________________
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    Regards,
    Don Rose, B.Mus., A.M.U.S., A.MUS., R.P.T.

    mailto:pianotuna@accesscomm.ca http://us.geocities.com/drpt1948/

    3004 Grant Rd.
    REGINA, SK
    S4S 5G7
    306-352-3620 or 1-888-29t-uner
    _______________________________________________
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