There are two kinds of movements: one-day (30-hour) and eight-day clockworks. Some have musical devices, and play a tune on a Swiss music box after striking the hours and half-hours. Usually the melody sounds only at full hours in eight-day clocks and both at full and half hours in the one-day timepieces. Musical cuckoo clocks frequently have other automata which move when the music box plays. Today’s cuckoo clocks are almost always weight driven, though a very few are spring driven. The weights are made of cast iron in a pine cone shape and the “cuc-koo” sound is created by two tiny gedackt pipes in the clock, with bellows attached to their tops. The clock’s movement activates the bellows to send a puff of air into each pipe alternately when the timekeeper strikes.