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Harmonic Shift?

  • 1.  Harmonic Shift?

    Posted 11-26-2017 13:26
    ​​At our last chapter (Seattle) meeting, a member demonstrated his new Electronic Tuning Device (ETD) program for Android phones. This program included a basic spectrum analyzer which displays the harmonic placement in a given string. The question is, does a string shift its harmonic placement (i.e. frequency shift), if only for a millisecond, given a soft or hard blow? If so, is this a component as to why electronic pianos sound so tonally "flat" compared to acoustic pianos?

    Roger Gable
    Gable Piano
    Everett WA

  • 2.  RE: Harmonic Shift?

    Posted 11-26-2017 21:14
    Roger, I am not sure what you mean, so I can't attempt an answer. Anthony Willey's program included discussions of Doppler shift, is that what you mean?

    Edward McMorrow
    Edmonds WA

  • 3.  RE: Harmonic Shift?

    Posted 11-27-2017 12:33
    If we start at A=440 and the second harmonic is 880 (for simplicity, lets not consider inharmonicity), do the ratio of harmonics rise momentarily within a millisecond of hammer impact to say, 880.1 and then drop back down to 880 during the traditional 2 – 5 second decay. All the spectrum analyzers I've seen have been measured way past the attack and somewhere in the decay period. I know my strobe will indicate an increase in overall pitch during attack (within milliseconds) and then drop back to the assigned pitch where we as technicians make pitch judgment.
    If this is true, that the harmonic ratios are slightly different on attack, it could be attributed to the momentary shortness of the speaking length caused by the hammer to bridge.
    Hope that clears up my question.

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  • 4.  RE: Harmonic Shift?

    Posted 11-27-2017 12:34

    Im not entirely sure what the scientific term for what you're describing is. But, I have noticed something similar. While giving myself a pretest of the tuning exam, I noticed that if I play the note a medium blow, then play a forte blow, the pitch of the second is a few hundredths of a cent sharper. Then if I go back to playing a medium blow, the pitch is the same as originally measured.

    Benjamin Sanchez
    Professional Piano Services