The action is complicated, and unless it works with the greatest accuracy it is worse than useless. Briefly, the principle consists in placing beneath the wrest-pin a small collar having two studs fastened on its " flat" similar to a " wing-nut," the whole working on a stud through the head. These are connected by a system of levers in head and pillar to the pedals, pressure upon which causes a partial revolution of these collars, between the studs of which the string passes, and is consequently tightened or raised in pitch. Various pedals are required; for instance, one for F sharps, another for C sharps, and so on, each pedal affecting only the notes of the same name throughout the instrument.