Iamblichus

The whole Pythagoric school produced certain appropriate songs, usefully conducting the dispositions of the soul to the passions contrary to those which it before possessed.  For when they went to bed they purified the reasoning power from the perturbations and noises to which it had been exposed during the day, by certain odes and peculiar songs, and by this means procured for themselves tranquil sleep, and few and good dreams.

But when they rose from bed, they again liberated themselves from the torpor and heaviness of sleep, by songs of another kind.  Sometimes also by musical sounds alone, unaccompanied with words, they healed the passions of the soul and certain diseases, enchanting, as they say, in reality.  And it is probable that from hence this name that enchantment  came to be generally used.  After this manner therefore, Pythagoras through music produced the most beneficial correction of human manners and lives.