Question

The Gloria is sung near the beginning of a Roman Catholic worship service known as the Mass. Other prayers and texts are spoken or chanted before and after it. The priest officiating at the service sings the opening of the Gloria. For that reason, the opening phrase you hear is sung by

Answer 1

One person (the Priest)

The Priest officiating the service beings the singing of Gloria. After the opening phrase, other voices join in. This means that the opening phrase is only sung by one voice.