The student should note the difference between groups 1 and 2 as given above: the terms in group 1 indicate that each measure, and even each pulse in the measure, is a little slower than the preceding one, while such terms as più lento and meno mosso indicate a rate of speed becoming instantly slower and extending over an entire phrase or passage. Some composers (e.g., Beethoven and Couperin) have evidently had this same distinction in mind between rallentando and ritardando on the one hand, and ritenuto and ritenente on the other, considering the former (rall. and rit.) to indicate a gradually slackening speed, and the latter (ritenuto and ritenente) to indicate a definitely slower rate. The majority of composers do not however differentiate between them in this way, and it will therefore hardly be worth while for the student to try to remember the distinction.
(b) Terms indicating a more rapid tempo.
1. Terms indicating a gradual acceleration.
Accelerando, affrettando (this term implies some degree of excitement also), stringendo, poco a poco animato.
2. Terms indicating a tempo which is to become definitely faster at once.
Più allegro, più tosto, più mosso, stretto, un poco animato.
112. After any modification in tempo (either faster or slower) has been suggested it is usual to indicate a return to the normal rate by some such expression as a tempo (lit. in time), a tempo primo (lit. in the first time), tempo primo, or tempo.
113. Tempo rubato (or a tempo rubato) means literally in robbed time, i.e., duration taken from one measure or beat and given to another, but in modern practice the term is quite generally applied to any irregularity of rhythm or tempo not definitely indicated in the score.
The terms ad libitum, (ad lib.), a piacere, and a capriccio, also indicate a modification of the tempo at the will of the performer. Ad libitum means at liberty; a piacere, at pleasure; and a capriccio, at the caprice (of the performer).
114. The term tempo giusto is the opposite of tempo rubato (and of the other terms defined in paragraph 113). It means literally in exact time. (Tempo giusto is sometimes translated quite rapidly,[29] but this is very unusual.)