TEMPO (Ital. time), the degree of rapidity with which a piece of music is to be exe cuted. The rhythmical proportions of notes, as indicated by their form, give them only a relative value, and have no reference to the absolute speed with which the composi tion should be played. Some compositions require, from their character, a quick lively movement; for others, a slower movement is more suitable; and different terms are used to indicate different gradations of movement. Of these the principal, beginning with the slowest, are: Largo, broad; lctrglietto, somewhat broad; lento, dragging; grave, heavy, solemn; adagio, slow; andantino, moving a little; andante, moving; allegretto, somewhat lively; moderato, moderately quick; allegro, lively; vivace, with vivacity;. presto, rapidly; prestissimo, with great rapidity. These terms are not always used with the precision that might be wished, and sometimes apply more to the character than to the absolute speed of performance. They are often modified by other qualifying words, as allegro con brio, lively and with briskness; allegro appassionnato, passionately excited.
The tempo is indicated with more exactness by a reference to the beat of the metronome (q.v.). Thus, INI.M..1-= 120, signifies that 120 beats of the metronome, each represent ing a crochet, are to fill up the space of a minute; M.M.4 = 60, that 60 quavers are to be performed in a minute.
While the general rule is, that the time of a movement is to be steady and unvary ing, cases often occur where a certain part of a composition has to be taken quicker or slower than the rest; this is indicated by such terms as pile vivo. more lively; or ritenuto, kept back; while a return to the original time is expressed by the words a tempo. The performer may be required to proceed from one degree of movement to another, not abruptly, but gradually; the time used to express this are: rilascieendo, slackening; ritar da nclo, retarding; calando, calming down; stringendo, pressing on; accelerando, gradually increasing speed; with some others.