JP Rameau on the properties of harmonies, 1722
From the Traité de l’harmonie 
OF THE PROPERTIES OF HARMONIES
It is certain that harmony can arouse in us passions, depending on the particular harmonies that are employed. There are harmonies that are sad, languishing, tender, agreeable, gay and striking; there are also certain successions of harmonies for the expression of these passions; and although it is quite foreign to my purpose I shall give of this as full an explanation as experience has given me.
Consonant harmonies are to be found everywhere abut should be employed mores frequently in music expressing gaiety and magnificence; and, since we cannot avoid intermingling some dissonant harmonies, we must contrive that these arise naturally, that they are far as possible prepared, and that the most prominent parts, the soprano and bass, are always consonant with respect to one another.
Sweetness and tenderness are sometimes well enough expressed by prepared minor dissonances.
Tender complaints sometimes require dissonances “by borrowing” and “by supposition,” rather minor than major, such major dissonances as may occur being confined rather to the inner parts that to the outer.
Languishing and sufferings are perfectly expressed by dissonances “by supposition” and especially by chromatic progressions, regarding which we shall speak in our next book.
Despair and all passions having to do with anger or which have anything striking about them require unprepared dissonances of every kind; above all, the major dissonances should be situated in the soprano. In certain expressions of this nature it is even effective to pass from one key to another by means of unprepared dissonances, yet in such a way that the ear is not offended by too great a disproportion; like all other such procedures, this can accordingly be carried out only with great discretion, for if we do nothing but pile dissonance on dissonace wherever there is place for it, it will be a much greater fault than only consonance to be heard. Dissonance, then, is to be employed with considerable discretion, and, when we feel that its harshness is not in agreement with the expression, we ought to avoid allowing it to be heard, in those harmonies that cannot do without it, by suppressing it adroitly, dispersing the consonances which make up the rest of the harmony through all the parts; for one ought always to bear in mind that the seventh, from which all the dissonances arise, is simply a sound added to the triad which does not at all destroy the basis of the harmony and may always be suppressed when we think it appropriate.
[Rameau discusses melody for two paragraphs.]
….a good musician ought to surrender himself to all the characters he wishes to depict and, like a skilful actor, put himself in the place of the speaker, imagine himself in the localities where the different events he wishes to represent occur, and take in these the same interest as those most concerned; he ought to be a good speaker, at least by nature; and he ought to know when the voice should be raised or lowered, by more or by less, in order to adapt to this his melody, his harmony, his modulation and his movement.
Strunk, Oliver, Source Readings in Music History, The Baroque Era. WW Norton & Company, New York and London, 1965. SBN 393-09682-3, pp. 212-214.