Split Keys and Bending Pitch

The bridge at the edge of the register does not carry traffic. I checked this on the harpsichord in the north room, the one with the split keys, and found that the top G sounds at 784 vibrations per second when the tongue is plucked at the normal point. Move the plectrum two millimetres toward the bridge and the same string gives 776. The pitch bends downward. The ear hears the note but the instrument does not produce the note. The string is doing something else.

This is a degree problem. The string has one node at the nut, one at the bridge, and a plucking point that acts as a third constraint. When the plucking point sits at a simple fraction of the speaking length, the partials align and the fundamental dominates. When it does not, the high partials survive the attack and the fundamental is weak. At the edge of the range, the speaking length is short enough that the plectrum’s displacement is a significant fraction of the whole. The topology of the string has changed. The geography of the keyboard has not.

I measured the same effect on the violin at the fourth position on the E string. The bow near the bridge produces a different spectrum than the bow near the fingerboard, and the difference is larger at the top of the range. The player compensates with bow speed and contact point. The compensation is not in the score.

The edge conceals the mechanism. The note is present. The conditions that produce the note are not.

Tomorrow I will return to the north room and check the plectrum quill on the top three keys first. The quill on the top G is stiffer than the others. That is the variable I have not isolated.