Pope Telephorus is accredited with establishing the custom of celebrating the Midnight Mass(for Christmas) beginning in 125 A.D. It is just a few more years (129 A.D.) that he began instituting songs for this Mass about angels.
Acts 20:7 states, “On the first day of the week, when we were gathered together to break bread, Paul talked with them, intending to depart on the morrow; and he prolonged his speech until midnight. There were many lights in the upper chamber where we were gathered. And a young man named Eutychus was sitting in the window. He sank into a deep sleep as Paul talked still longer; and being overcome by sleep, he fell down from the third story and was taken up dead. But Paul went down and bent over him, and embracing him said, ‘Do not be alarmed, for his life is in him. And when Paul had gone up and had broken bread and eaten, he conversed with them a long while, until daybreak, and so departed. And they took the lad away alive, and were not a little comforted”.
Here is a written record of someone falling asleep during one of St. Paul’s sermons. God was able to show his favor with St. Paul through this as the boy fell out of a third story window. In this case, St. Paul was going to be leaving so this was a late service. Midnight Mass is late, but it is ushering in the day of Christmas. This tradition would branch throughout the Christian world as the Church would survive terrible persecutions.
Singing on Christmas Eve was symbolic of the shepherds who kept vigil over the flocks when the angels announced the good news, “Glory to God in the highest and on earth peace to those on whom his favor rests” (Luke 2:14).