Plutarch Quaestiones Convivales 1.5.2

[2] Sossius applauding these discourses added: Perhaps we may make a probable conjecture from Theophrastus’s discourse of Music, for I have lately read the book. Theophrastus lays down three causes of music,—grief, pleasure, and enthusiasm; for each of these changes the usual tone, and makes the voice slide into a cadence; for deep sorrow has something tunable in its groans, and therefore we perceive our orators in their conclusions, and actors in their complaints, are somewhat melodious, and insensibly fall into a tune. Excess of joy provokes the more airy men to frisk and dance and keep their steps, though unskilful in the art; and, as Pindar hath it, But the graver sort are excited only to sing, raise their voice, and tune their words into a sonnet. But enthusiasm quite changes the body and the voice, and makes it far different from its usual constitution. Hence the very Bacchae use measure, and the inspired give their oracles in measure. And we shall see very few madmen but are frantic in rhyme and rave in verse. This being certain, if you will but anatomize love a little, and look narrowly into it, it will appear that no passion in the world is attended with more violent grief, more excessive joy, or greater ecstasies and fury; a lover’s soul looks like Sophocles’s city: And therefore it is no wonder, that since love contains all the causes of music,—grief, pleasure, and enthusiasm,—and is besides industrious and talkative, it should incline us more than any other passion to poetry and songs.