This is one of the most fascinating and difficult complications in modern mechanical watchmaking. Unlike the passage chime, which is still found in clocks today and which provides for one chime at one o'clock, two at two o'clock and so on up to twelve chimes at twelve o'clock, the minute repeater allows the hours, quarters and minutes to be chimed on command. The chime is usually activated by moving a slider on the side of the case with a finger: when the slider is operated, a spring is wound up which, as it unwinds, releases the energy required for the hammers to strike. These, beating one at a time or simultaneously on the ring-shaped metal gongs that run around the circumference of the case, can produce different tones of sound: one grave sound for each hour, two sounds in rapid sequence for each quarter-hour and a high-pitched sound for the missing minutes. If, for example, the clock strikes 2:33, there will be two sounds for the hours, two for the quarter-hours and three sounds for the three minutes in excess. Another device then ensures that the chimes are not too fast, otherwise one would not have time to count them. The greatest difficulty encountered in the construction of these clocks is related to the need to obtain a clean and loud sound while maintaining the small size of the case. The care and attention primarily concerns the steel alloy used for the gongs and the arrangement of the movement inside the case, which allows the gongs to resonate throughout their length. The Bulgari Octo Finissimo Minute Repeater features a push-button on the left side of the case to activate the striking mechanism. The sound is amplified by the openings on the dial and the choice of titanium for the case, a material that guarantees the best possible sound diffusion.
