Principi Apostolorum Petro §12

¹² It is indeed fitting to honor the blessed deacon of Edessa for his desire that the preaching of the divine word and the training of his disciples rest on the purity of Sacred Scripture. He also acquired honor as a Christian musician and poet. He was so accomplished in both arts that he was called the "lyre of the Holy Spirit." From this, Venerable Brothers, you can learn what arts promote the knowledge of sacred things. Ephrem lived among people whose nature was attracted by the sweetness of poetry and music. The heretics of the second century after Christ used these same allurements to skillfully disseminate their errors. Therefore Ephrem, like youthful David killing the giant Goliath with his own sword, opposed art with art and clothed Catholic doctrine in melody and rhythm. These he diligently taught to boys and girls, so that eventually all the people learned them. In this fashion he not only renewed the education of the faithful in Christian doctrine and supported their piety with the spirit of the sacred liturgy, but also happily kept creeping heresy at bay.