music, is justly defined by Rousseau to be the invention and the conduct of the subject, the disposition of every part, and the general order of the whole.

It is not sufficient to form beautiful airs, and a legitimate harmony; all these must be connected by a principal subject, to which all the parts of the work relate, and by which they become one. Thus unity ought to prevail in the air, in the movement, in the character, in the harmony, and in the modulation. All these must indispensably relate to one common idea which unites them. The greatest difficulty is, to reconcile the observation of those precepts with an elegant variety, which, if not introduced, renders the whole piece irksome and monotonic. Without question, the musician, as well as the poet and the painter, may risk every thing in favour of this delightful variety; if, under the pretext of contrasting, they do not endeavour to cheat us with false appearances, and instead of pieces justly and happily planned, present us with a musical minced-meat, composed of little abortive fragments, and of characters so incompatible, that the whole assembled forms a heterogeneous monster.

Non ubi placidus coquit immitis, non ubi Serpentes ovibus gimmentur, ligibris agit.

Translated thus:

But not that nature should rever'd appear; Mix mild with fierce, and gentle with severe; Profane her laws to contradiction's neighr; Tygers with lambs, with serpents birds unite.

It is therefore in a distribution formed with intelligence and taste, in a just proportion between all the parts, that the perfection of design consists; and it is above all, in this point, that the immortal Pergolesi has shown his judgment and his taste, and has left so far behind him all his competitors. His Stabat Mater, his Orfeo, his Serva Padrona, are, in three different species of composition, three masterpieces of design equally perfect.

This idea of the general design of a work is likewise particularly applicable to every piece of which it consists; thus the composer plans an air, a duet, a chorus, &c. For this purpose, after having invented his subject, he distributes it, according to the rules of a legitimate modulation, into all the parts where it ought to be perceived, in such a proportion, that its impression may not be lost on the minds of the audience; yet that it may never be reiterated in their ears, without the graces of novelty. The composer errs in designing who suffers his subject to be forgot; he is still more culpable who pursues it till it becomes trite and tiresome.