String changing pitch with volume?

  • Participant
    unknown-user on #150864

    Hi all,

    I’ve just noticed recently that the harder I pluck my low C (lowest on a concert grand) the higher pitched it gets. If I pluck it anywhere up to and including about “mp,” it plays one note; however, if I pluck it louder, it suddenly starts sounding nearly a semitone higher. Has anyone experienced this? Is it an audio illusion? Is this just something I need to live with or might there be a problem?

    Thanks,

    Sam

    Member
    kay-lister on #150865

    Hi Sam,

    I’ve never noticed anything like that so I’m just guessing here.

    Participant
    bernhard-schmidt on #150866

    Hi Sam,

    No this is not an audio illusion…..
    This happens often but more

    Participant
    bernhard-schmidt on #150867

    OK, I will try to explain…

    When you pluck the string very hard…..what is happend to the string at the moment you pluck ?

    The string is getting longer by stretching the string and by this the tension of the string is getting higher ….the result is a higher pitch.
    This will happen to all plucked strings.

    Participant
    unknown-user on #150868

    Bernhard-

    That could be it, but with my limited knowledge of string physics, I would guess that when one pulls on a string (like just before when one plucks it) the tension and length change would actually cancel each other and it would resonate at the correct pitch the entire time. But, like I said, my knowledge is limited and perhaps you are more qualified to answer such a question. Also, I am not hearing the pitch falling as the sound decays: I can hear two distinct pitches depending on how hard I pluck the string, but they do not decay. Additionally, if your theory was true, I would hear this phenomenon when I pluck other strings, and I do not.

    Perhaps the string is creating some strange overtones? I’d rather not change the string, though, until I rule anything else out.

    Sam

    Participant
    carl-swanson on #150869

    Bernhard- Your explanation makes sense. I have noticed the same effect that Sam describes but frankly never worried about it. It’s just one of those things that happens on harps.

    I use a strobe tuner to tune and regulate harps, and depending on how hard I pluck the string, the pitch can initially read high then settle to something lower. This is why it can be tricky regulating a harp. I always like to have the harpist check things afterwards while I am still there. If her/his touch is very different from mine, the regulation adjustments, particularly in the upper octaves, could be different. Plucking a string in the first octave for example either softly or loud can produce very different pitches. It’s even worse if the tuning pins are too far from the string bridge(as one major company did for many years) resulting in a “dead” string length(the section of string between the string bridge, or string nut, and the tuning pin) that is longer than the “live” string length( the part that you pluck). On those instruments, if you pluck a first or second octave string hard, the pitch will drop by as much as 1/4 step and has to be tuned up to pitch again. A technician regulating such a harp can’t regulate out that problem. Several times over the years I’ve had to replace what were otherwise perfectly good necks because of this problem.

    Participant
    bernhard-schmidt on #150870

    Sam,
    “…..Also, I am not hearing the pitch falling as the sound decays: I can hear two distinct pitches depending on how hard I pluck the string, but they do not decay…….”
    In this case it

    Member
    jennifer-buehler on #150871

    Bernhard and Carl

    Does it make a difference what the string is made of?

    Participant
    carl-swanson on #150872

    Jennifer- You may not have an option. I don’t know what kind of harp you have, but you may have to use a very low tension string there. I suspect that the issue is that the wider the swing of the string when it is plucked, the greater the distortion of the pitch. This is why Sam noticed this in the lowest strings on his pedal harp and why it is generally less of a problem the higher you go on the instrument. The harder you pull that string, the more it is going to distort the sound.

    Member
    jennifer-buehler on #150873

    I’d have to pull out my string chart to look but it is pretty low tension.

    Participant
    bernhard-schmidt on #150874

    Yes, this problem of Jenniver should be because a string with low tension.
    Low tension by itself is not the problem but in your case it should be to low tension for the string.
    A bass string should have at least something around 35 % (so more high so better it is) of the breaking point (The tension where the string break)

    This means a string construction need at least a certain tension to give a good sound.

    But to your question….yes with a different string composition related to the lower tension of your harp there should be a possibility to improve the sound of this note.

    This is a very known problem to all harps with a not wery well ballanced string tension.

    Member
    jennifer-buehler on #150875

    Thanks Carl and Berhard

    Participant
    Saul Davis Zlatkovski on #150876

    When you bend the string, you bend the pitch. Over-pulling the string will produce that effect. Generally speaking, it is not really desirable.

    Participant
    unknown-user on #150877

    The problem fixed itself after the string was changed and the harp was regulated. It was not an over-bending affect, which many insisted it was, despite evidence against it, rather a strange buzz that was close to the pitch of the string, making the pitch seem off. It would buzz louder the harder the string was plucked, and so the problem was worsened when the string was played loudly. Thank goodness for regulators! 🙂

    ~Sam

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