The general inferiority of operatic libretti has occasioned the musical drama to be despised as a branch of literature; although, to say nothing of the recent achievements of Richard Wagner, the Euripidean play, with its frequent predominance of solos over choral parts, approximated to the modern opera. It is no doubt true that the first requisite is that the words should be a vehicle for the music, and that, supposing this object attained, it is feasible to dispense with poetry. It follows that poetry usually is dispensed with, and that the only literary gift deemed absolutely indispensable for opera is that of dramatic construction. It is the great distinction of Metastasio to have been at the same time a consummate playwright and a true lyrical poet. Other great playwrights have been great poets in blank verse; but, at any rate for the first half of his life, Metastasio’s bosom was as affluent a storehouse of melody as Rückert’s; to sing was for him as easy as to speak. He was constrained to submit himself to the laws of the opera, inexorable because founded upon the reason of things. As an opera can be nothing without a _cantatrice_, it follows that it must turn chiefly upon the passion of love; as the principal performers’ throats will not bear a perpetual strain, they must necessarily be sometimes relieved by inferior executants; hence the necessity of an underplot, and of constructive ability to interweave this with the main action. As the musical drama is not, after all, natural, the audience’s attention must be kept occupied by continual action and bustle; as the singer must leave the stage at his best, the recitative must be followed by an air. Such tags must be judged simply with reference to the musical effect, which with Metastasio was always very great. On the whole, few writers have adapted means to ends more successfully than he has done, or have more completely solved the problem of investing the amusement of the moment with abiding literary worth.