The tempo is an indicator of the speed at which a piece is to be performed. It is expressed most precisely in beats per minute, but often a composer will simply provide more general direction to the performer. These directions can be in a variety of different languages. They may be clear and concise, or they may be more descriptive or open to interpretation.
In classical music, tempo markings are frequently provided in Italian. Later, composers began providing direction in their own language, so performers need some fluency in Italian, German, French, and English to interpret indications provided by a broad range of composers.
The most basic terms simply convey the general speed. “Grave,” “Largo,” “Lento,” and “Adagio” direct the performer to play the piece slowly. There are no fixed rules for precisely how slowly the music should be played – this will depend on convention, musical taste, and clues provided by the composer in other aspects of the music. However, a reasonable interpretation might be around 50-70 beats per minute – again, depending on the context. Interpretation is subjective, but the speed ultimately must be appropriate in order for the audience to properly understand the music.
“Andante,” “Moderato,” and “Allegretto” indicate more moderate speeds – perhaps 80-120 beats per minute. “Allegro,” “Vivace,” and “Presto” direct the performer to play fast. Tempos can change in the middle of a piece, too. “Ritardando” (often abbreviated as “rit.” or “ritard.”) directs the performer to slow down, and “Accelerando” (“accel.”) means speed up.
Sometimes, composers will want to also provide a qualification or indication of the intended mood alongside tempo markings. “Subito” means “suddenly” – direction to do something immediately, with tempo or dynamics. “Poco” means a little – for instance, “poco allegro” would be “a little fast.” “Poco a poco” means “little by little.” For mood, common terms include “cantabile” (like singing, lyrical), “dolce” (sweetly), “espressivo” (expressively), “animato” (lively), and “pesante” (heavily). Mood indicators are highly subjective, and the best interpretations will consider all of the individual components of the music – tempo, dynamics, articulation, harmony, melody, rhythm.
Tempo is an extremely important element of any composition. It sets the tone from the get-go: a piece may be slow and plodding, moderate and pensive, or fast and cheerful. The audience will immediately get a sense of the character of the music. But it is only one element, and it must work cohesively and coherently with all others.