The metronome is a device, formerly based on the principle of the pendulum, but now controlled more often by electronic means, which measures the equal beats of a piece of music, as a guide to players. The metronome mark of 60 indicates one beat a second, 120 is twice as fast and 240 twice as fast again. The principle was based on the work of Galileo, but the most frequently found clockwork metronome was devised in Vienna by Beethoven's contemporary and briefly his collaborator Count Maelzel.