"Not long had the Church of Milan begun to employ this kind of consolation and exhortation, the brethren singing together with great earnestness of voice and heart. For it was about a year, or not much more, since Justina, the mother of the boy-Emperor Valentinian,persecuted Your servant Ambrose in the interest of her heresy, to which she had been seduced by the Arians. The pious people kept guard in the church, prepared to die with their bishop, Your servant. There my mother, Your handmaid, bearing a chief part of those cares and watchings, lived in prayer. We, still unmelted by the heat of Your Spirit, were yet moved by the astonished and disturbed city. At thistime it was instituted that, after the manner of the Eastern Church, hymns and psalms should be sung, lest the people should pine away in the tediousness of sorrow; which custom, retained from then till now, is imitated by many, yea, by almost all of Your congregations throughout the rest of the world."
From Confessions of St. Augustine, book 9, ch. 7.15