Plato on Music
Then to sum up: This is the point to which, above all, the attention of our rulers should be directed, --that music and gymnastic be preserved in their original form, and no innovation made. They must do their utmost to maintain them intact. And when any one says that mankind most regard
The newest song which the singers have, they will be afraid that he may be praising, not new songs, but a new kind of song; and this ought not to be praised, or conceived to be the meaning of the poet; for any musical innovation is full of danger to the whole State, and ought to be prohibited. So Damon tells me, and I can quite believe him;-he says that when modes of music change, of the State always change with them.
Yes, said Adeimantus; and you may add my suffrage to Damon's and your own.
Then, I said, our guardians must lay the foundations of their fortress in music?
Yes, he said; the lawlessness of which you speak too easily steals in.
The Republic, Book 4 - Plato (p. 312)