Metronome
Beat-measuring device calibrated after Mälzel.
What it means
The metronome is a device that produces even beats at an adjustable speed and thereby makes a tempo audible. The indication is given in beats per minute, related to a particular note value: “♩ = 72” means 72 quarter notes per minute. The traditional construction with pendulum and weight carries the name of its populariser Mälzel, from which the common abbreviation M.M. derives; alongside it there are electronic devices and applications.
Musical use
With the metronome it became possible for the first time to state a tempo unambiguously. Before that, only the Italian designations were available for this, which name a character and an approximate tempo but leave room for latitude — and deliberately leave that latitude open.
Metronome markings nonetheless need to be handled with care. Not all markings printed in editions come from the composer; many were added by editors. With some transmitted markings from the nineteenth century it is also debated whether they are meant as they are read today. And even a well-established marking describes a tempo, not the shaping: a movement played consistently exactly on the metronome beat generally seems rigid, because phrase endings, climaxes, and transitions demand small stretchings.
In older music such markings are entirely absent; there the tempo results from the type of metre, the smallest note values occurring, the character, and, with dances, from the underlying movement.
The metronome was patented in 1815 by Johann Nepomuk Mälzel, who thereby drew on an invention by Dietrich Nikolaus Winkel. Beethoven was among the first composers to enter metronome markings into his works; many of his markings are still discussed controversially today. The abbreviation M.M. stands for Mälzel's Metronome.
Performance practice
Use the metronome for checking, not for accompanying: check with it whether a passage is even, and then play it without. Practise difficult passages slowly and increase in small steps. Occasionally set it so that it beats only on every second beat or only on the downbeat — this trains the inner sense of time far better than a beat on every note.