> I theorize > that some distortion of the sound wave occurs with a harder blow, which > would seem to make it more difficult to tune precisely. However, that is > just my theory--does anyone have any data on this? One direct, sharp blow is sufficient. While gently manipulating the tuning pin, you are pulling the short distance between pressure bar and tuning pin into much higher tension than the tension on the speaking distance of the string. The purpose of the hard blow is to equalize these two tensions. If they are not equalized at the time of tuning, they will equalize more slowly (and the piano will go out of tune rapidly).
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