Careful consideration has been give to the design of the jacks since it is the jacks which give the strings their energy and therefore many of their acoustical and musical properties. The mechanical properties of the jack, tongue, quill and damper are therefore very important indeed to the sound of the instrument, and also to the way the instrument functions mechanically. Therefore each aspect of the jack design was given separate consideration. The position of the axle pin of the tongue, for example, should be neither too high nor too low in the jack. If it is too high then there is very little leverage of the spring against the top section of the tongue. If the axle is too low, on the other hand, the leverage of the tongue spring is large, but the tongue itself then may vibrate in the slot and therefore not repeat properly in fast passagework. The position of the axle was therefore based on the position of a number of different historical Neapolitan instruments with original jacks which seemed to function well.