Divine Office in Augustine

I am embarking on my annual reading of the Confessions of St. Augustine of Hippo. In book nine, which recounts his immersion in the regenerative waters of Baptism and his early days as a Catholic, he describes what is most likely the origin of the Ambrosian Office:

"And how I cried out to you, my God, when I read the Psalms of David, those songs of faith, whose pious music will not admit the haughty spirit, while yet untutored in your true love and a catechumen...." (9.4.8)

"Nor, during those days, could I be satiated with the wondrous sweetness of contemplating the depth of your counsel for the salvation of mankind. How  wept at the hymns and sacred songs of your Church, how moved was I at its tuneful voices! Those voices flowed in through my ears, and the truth, pressed and trained out of them, entered my heart and from my heart a pious longing came boiling up and overflowed. My tears ran; I wept, and it was well with me.

" It was not long since the Church at Milan had instituted this manner of strengthening and encouraging themselves, with brothers thronging together, full of zeal, singing with voices and hearts in harmony. There was a year, not much more, during which Justina, mother of the boy king Valentinian, was persecuting Ambrose, the man of God, in the interests of her own heresy; she had been seduced by the Arians. The devout populace mounted watch in the church, ready to die with their bishop, your servant. My mother, your handmaid, was there, and took her stand as one of the foremost in those anxious vigils, living on prayers. I too, though as yet unwarmed by the heat of your Spirit, was none the less excited by the consternation and uproar in the city. It was then that the custom was established of singing hymns and psalms after the Eastern fashion, to keep the people from growing weary and faint-hearted; and the custom then established has been maintained, and many if not all your flocks throughout the rest of the world have imitated it." (9.6.14-9.7.15)