metronome

1. (music) A device, containing an inverted pendulum, used to mark time by means of regular ticks at adjustable intervals; an electronic equivalent that emits flashes.Examples: "The etudes with metronome markings should be played in tempo, all others should be considered rubato."; "It’s one of the earliest pieces in the comprehensive collection of metronomes by the British instrument dealer Tony Bingham, which forms the bulk of the Basel exhibition."