Text: An instrument of steel with two prongs, which when set in vibration gives out a musical sound varying in pitch according to the thickness of the metal or the length or width apart of the prongs. It was invented by John Shore, sergeant trumpeter to George I. There is a considerable variety in the pitch of tuning forks, arising from the absence of any recognised standard of tonality. The ordinary fork gives out a single note only, but one has been introduced from Germany which has a slider on each prong which can be moved up or down so as to alter the pitch. (A Dictionary of Musical Terms)

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Source: 125