A metronome is any device that produces regular, metrical ticks (beats, clicks) — settable in beats per minute. These ticks represent a fixed, regular aural pulse; some metronomes also include synchronized visual motion (e.g. pendulum-swing). The metronome dates from the early 19th century, where it was patented by Johann Maelzel in 1815 as a tool for musicians, under the title "Instrument/Machine for the Improvement of all Musical Performance, called Metronome".
In the 20th century and especially today the metronome is generally positively regarded in Europe and Western culture. The metronome is used by some musicians for practice in maintaining a consistent tempo with steady regular beats and it can be used by composers, as an approximate way of specifying the tempo.
Yet in stark contrasting with this postivistic view, research on the history of the metronome and its influence on performance practice, reveals criticisms of metronome use, and highlights differences of "performance practice" and cultural perception/values between the current modern European/Western society (which values the metronome), and the same society during previous times (beginning of the 19th century and earlier: classical/romantic/baroque eras etc.).
Accordingly, some musicians consider the metronome to be a highly controversial tool in regard to music, with some rejecting the metronome altogether. Some composers considering metronome-tempo-marks to have only little value, or to hinder creative musical interpretation: Johannes Brahms said: "I am of the opinion that metronome marks go for nothing. As far as I know, all composers have, as I, retracted their metronome marks in later years."