A Dictionary of Music and Musicians/Rallentando
RALLENTANDO, RITARDANDO, RITENENTE, RITENUTO—'Becoming slow again,' 'Slackening,' 'Holding back,' 'Held back.' The first two of these words are used quite indifferently to express a gradual diminution of the rate of speed in a composition, and although the last is commonly used in exactly the same way, it seems originally and in a strict sense to have meant a uniform rate of slower time, so that the whole passage marked ritenuto would be taken at the same time, while each bar and each phrase in a passage marked rallentando would be a little slower than the one before it. That there exists a difference in their uses is conclusively proved by a passage in the Quartet op. 131 of Beethoven, where in the 7th movement (allegro) a phrase of three recurring minims, which is repeated in all five times, has the direction 'Espressivo, poco ritenuto' for its first three appearances, which are separated by two bars a tempo, and for the last two times has ritardando, which at length leads into the real a tempo, of which the former separating fragments were but a presage. This is one of the very rare instances of the use of the word ritenuto by Beethoven. The conclusion from it is confirmed by a passage in Chopin's Rondo, op. 16, consisting of the four bars which immediately precede the entry of the second subject. Here the first two bars consist of a fragment of a preceding figure which is repeated, so that both these bars are exactly the same; the last two bars however have a little chromatic cadence leading into the second subject. The direction over the first two bars is 'poco ritenuto' and over the last two 'rallentando,' by which we may be quite sure that the composer intended the repeated fragment to be played at the same speed in each bar, and the chromatic cadence to be slackened gradually.
Ritenente is used by Beethoven in the PF. Sonata, op. 110, about the middle of the first movement, and again in the Sonata, op. 111, in the first movement, in the seventh and fifteenth bars from the beginning of the Allegro con brio. It would seem that the same effect is intended as if 'ritenuto' were employed; in each case, the words 'meno mosso' might have been used. Beethoven prefers Ritardando to Rallentando, which latter is common only in his earlier works.