There had been times when a person possessing a copy of the Creed could have been martyred for having it.
Candidates also learned the Lord's Prayer. In one of the final scrutinies, those preparing for baptism (in Latin, called the competentes - meaning "seekers") were allowed into a special Eucharist to see their sponsors receive Communion, which they themselves would receive at the Mass of the Easter Vigil immediately after their baptism.
This was probably the first Mass that the competentes had witnessed right through.
Previously they would have only been permitted to be present for the Liturgy of the Word.
(This for the obvious reasons was inappropriately sometimes called the Mass of the Catechumens, even up to the time just before the Second Vatican Council forty years ago.)
During Lent the competentes
would have been fasting. In the Easter Vigil ceremony, the competentes
entered the church in procession with the clergy and Bishop Ambrose
They moved amidst a sea of candle flames, and were swept along by the congregational singing of the psalms.
Augustine described the unforgettable scene. He alluded to his own great appreciation of music and liturgy: "And so we were baptised .... What tears I shed in your hymns and canticles! How deeply was I moved by the voices of your sweet singing Church. Those voices flowed into my ears and the truth was distilled into my heart, which overflowed with my passionate devotion. Tears ran from my eyes and happy I was in those tears." (Confessions 9, 193-194)