ὁ δὲ πείσεται εἰς ἀγαθόν περ → he will obey you to his profit, he will obey you for his own good end
a sound: V. ἀντιφθέγγεσθαι, ἀνταλαλάζειν; see echo.
reecho (a sentiment): use P. and V. ἐπαινέω, ἐπαινεῖν; see approve.