Descriptive of the arrangement of pins in a barrel-operated instrument, with the pins arranged in a continuous helix. The barrel continuously shifts sideways as it turns, keeping the keys aligned with the key frame. In this way a long selection (sometimes comprising six or more revolutions of the barrel) may be played without interruption. 2. Helicoidal music box: a cylinder music box with the cylinder pinned in a helicoidal manner instead of the usual manner which requires the cylinder to be shifted in successive steps. In a semi-helicoidal music box, the cylinder is pinned diagonally only at the normal shifting area, permitting music to be pinned across the shifting gap which is normally silent.
MBSI
Musical Box Society International