Metronome

A metronome is a device that produces audible clicks or other signals at a steady, user-set tempo, usually measured in beats per minute, used by musicians, dancers and athletes to keep steady time. The Andalusian polymath Abbas ibn Firnas is credited with an early version of the device around the 9th century, and the German inventor Johann Maelzel patented the modern mechanical wind-up metronome, built around a swinging weighted pendulum, on December 5, 1815, describing it as an instrument for the improvement of musical performance. Maelzel's design became the standard reference for tempo in written music, with composers marking a piece's intended speed in metronome beats per minute, and electronic and software metronomes have since supplemented the original mechanical clockwork form.