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In musical terminology, tempo (Italian for time, movement) is the speed or pace of a given piece. It is a crucial element of composition, as it can affect the mood and difficulty of a piece. The plural of tempo is tempi.

Measuring tempo

The tempo of a piece will typically be written at the start of a piece of music, and in modern music is usually indicated in beats per minute (BPM). This means that a particular note value (for example, a quarter note or crotchet) is specified as the beat, and the marking indicates that a certain number of these beats must be played per minute. The greater the tempo, the larger the number of beats that must be played in a minute is, and, therefore, the faster a piece must be played. Mathematical tempo markings of this kind became increasingly popular during the first half of the 19th century, after the metronome had been invented by Johann Nepomuk Mälzel, although early metronomes were somewhat inconsistent. Beethoven was the first composer to use the metronome, and in 1817 he published metronomic indications for his (then) eight symphonies. Unfortunately, the metronome markings on his "Hammerklavier" Sonata and Ninth Symphony are almost impossibly fast, as is also the case for many of the works of Schumann.

With the advent of modern electronics, BPM became an extremely precise measure. MIDI files and other types of sequencing software use the BPM system to denote tempo.

As an alternative to metronome markings, some 20th century composers (such as Béla Bartók and John Cage) would give the total execution time of a piece, from which the proper tempo can be roughly derived.

Tempo is as crucial in contemporary music as it is in classical. In electronic dance music, accurate knowledge of a tune's BPM is important to DJs for the purposes of beatmatching.

Musical vocabulary for tempo

Whether a music piece has a mathematical time indication or not, in classical music it is customary to describe the tempo of a piece by one or more words. Most of these words are Italian, because many of the most important composers of the 17th century were Italian, and this period was when tempo indications were first used extensively.

Before the metronome, words were the only way to describe the tempo of a composition. Yet after the metronome's invention, these words continued to be used, often additionally indicating the mood of the piece, thus blurring the traditional distinction between tempo and mood indicators. For example, presto and allegro both indicate a speedy execution (presto being faster), but allegro also connotes joy (from its original meaning in Italian). Presto, on the other hand, indicates speed as such (while possibly connoting virtuosity, a connotation it did not acquire until the late 18th century).

Additional Italian words also indicate tempo and mood. For example, the "agitato" in the Allegro agitato of the last movement of George Gershwin's piano concerto in F has both a tempo indication (undoubtedly faster than a usual Allegro) and a mood indication ("agitated").