A metronome is a mechanical or electronic device that can be set to produce regular clicks, settable in beats per minute. This pulse is useful to allow the musician to play at the correct speed when practising. In the traditional mechanical metronome, the pendulum when moving from side to side (thus creating the click) also acts as a visual aid. In the digital version, a blinking LED light can serve the same purpose. More sophisticated models can use a different tone to emphasise the first beat of the bar.