The mechanical metronome drives a pendulum with the help of a spring. The desired speed is set using a weight on the pendulum. To the left and right of the pendulum is the scale with the beats per minute. The further you push the weight up on the pendulum, the slower the metronome counts in the beat. Each click falls to the value of a quarter note. The mechanical metronome works like a mechanical clockwork. To start it up, the spring must be wound with the help of a wrench. In order for it to work precisely, it has to stand on an exactly flat surface, as any inclination affects the swing of the pendulum.