metronome

The patent for the metronome was entered in 1816: "John Malzl [sic], of Poland-street, Middlesex, Machinist; for an instrument . . . which he denominates a Metronome, or musical time-keeper." The courts, however, later proved that the aforementioned Johann Maelzel copied a pendulum design of Dietrich Winkel, making Winkel the actual inventor. Nonetheless, Maelzel was the more successful marketer of the metronome and even has a notation named after him. The "M.M." in notations like "M.M. = 60" stands for "Maelzel's metronome" and indicates a tempo of 60 beats per minute or a beat per tick of the metronome as it ticks 60 times, in the case of our example. The name of the invention itself is based on the Greek words metron, meaning "measure," and nomos, meaning "law."