Metronome

A metronome (from Ancient Greek μέτρον (métron) 'measure' and νόμος (nómos) 'law') is a device that produces an audible click or other sound at a uniform interval that can be set by the user, typically in beats per minute (BPM). Metronomes may also include synchronized visual motion, such as a swinging pendulum or a blinking light. Musicians—and others including dancers, athletes, and health professionals—often practise with a metronome to improve their timing, especially the ability to maintain a steady tempo with a regular beat or pulse. Composers and conductors often use numerical metronome markings to communicate their preferred tempos to musicians preparing for a performance.

A type of metronome was among the inventions of Andalusian polymath Abbas ibn Firnas (810–887). In 1815, German inventor Johann Maelzel patented a mechanical, wind-up metronome as a tool for musicians, under the title "Instrument/Machine for the Improvement of all Musical Performance, called Metronome". In the 20th century, electronic metronomes and software metronomes were invented.

When interpreting emotion and other qualities in music, performers seldom play exactly on every beat. In a musically expressive performance, the pulse generally does not align with the clicks of a metronome. This has led some musicians to criticize use of a metronome, because "musical time is replaced by clock time".