A very useful device for many instrumentalists and musicians, in particularly string players, is a metronome. A mechanical metronome is a box like object that produces a steady beat. A musician sets this beat based on the tempo marking of the piece which they are practicing, and then the beats produced by the metronome help the musician to play at a steady pace and to avoid rushing or slowing. So, how does a metronome work? Well, from the outside, a metronome actually appears like an upside down pendulum; at the top there is a weight which is attached to the bottom of the box by a long rod. The musician can adjust the speed of the beats produced by lowering or raising this top weight. The way the metronome works is that at the bottom of this rod (and usually hidden from view) is a weight that acts like the bottom bob of a pendulum. So, when the instrumentalist lowers or raises the upper weight, they are in essence shortening or lengthening the length of the pendulum, hence increasing or decreasing the frequency of the simple harmonic motion and the tempo of the produced beats.