Even before Metastasio, Apostolo Zeno had, as it is called, purified the opera, a phrase which, in the sense of modern critics, often means emptying a thing of all its substance and vigour. He formed it on the model of Tragedy, and more especially of French Tragedy; and a too faithful, or rather too slavish approximation to this model, is the very cause why he left so little room for musical development, on which account his pieces were immediately driven from the stage of the opera by those of his more expert successor. It is in general an artistic mistake for one species to attempt, at evident disadvantage, that which another more perfectly accomplishes, and in the attempt, to sacrifice its own peculiar excellencies. It originates in a chilling idea of regularity, once for all established for every kind alike, instead of ascertaining the spirit and peculiar laws of each distinct species.
Metastasio quickly threw Zeno into the shade, since, with the same object in view, he displayed greater flexibility in accommodating himself to the requisitions of the musician. The merits which have gained for him the reputation of a classic among the Italians of the present day, and which, in some degree, have made him with them what Racine is with the French, are generally the perfect purity, clearness, elegance, and sweetness of his language, and, in particular, the soft melody and the extreme loveliness of his songs. Perhaps no poet ever possessed in a greater degree the talent of briefly bringing together all the essential features of a pathetic situation; the songs with which the characters make their exit, are almost always the purest concentrated musical extract of their state of mind. But, at the same time, we must own that all his delineations of passion are general: his pathos is purified, not only from all characteristic, as well as from all contemplative matter; and, consequently, the poetic representation, unencumbered thereby, proceeds with a light and easy motion, leaving to the musician the care of a richer and fuller development. Metastasio is musical throughout; but, to follow up the simile, we may observe, that of poetical music, melody is the only part that he possesses, being deficient in harmonious compass, and in the mysterious effects of counterpoint. Or, to express myself in different terms, he is musical, but in no respect picturesque. His melodies are light and pleasant, but they are constantly repeated with little or no variation: when we have read a few of his pieces, we know them all; and the composition as a whole is always without significance. His heroes, like those of Corneille, are gallant; his heroines tender, like those of Racine; but this has been too severely censured by many, without a due consideration of the requirements of the Opera. To me he appears censurable only for the selection of subjects, whose very seriousness could not without great incongruity be united with such triflings. Had Metastasio not adopted great historical names--had he borrowed his subject-matter more frequently from mythology, or from still more fanciful fictions--had he made always the same happy choice as that in his _Achilles in Scyros_, where, from the nature of the story, the Heroic is interwoven with the Idyllic, we might then have pardoned him if he invariably depicts his personages as in love. Then should we, if only we ourselves understood what ought to be expected from an opera, willingly have permitted him to indulge in feats of fancy still more venturesome. By his tragical pretensions he has injured himself: his powers were inadequate to support them, and the seductive movingness at which he aimed was irreconcileable with overpowering energy. I have heard a celebrated Italian poet assert that his countrymen were moved to tears by Metastasio. We cannot get over such a national testimony as this, except by throwing it back on the nation itself as a symptom of its own moral temperament. It appears to me undeniable, that a certain melting softness in the sentiments, and the expression of them, rendered Metastasio the delight of his contemporaries. He has lines which, from their dignity and vigorous compression, are perfectly suited to Tragedy, and yet we perceive in them an indescribable something, which seems to show that they were designed for the flexible throat of a soprano singer.