In the Liturgy, the Credo was first used as an individual’s profession of faith at Baptism. The Nicene Creed was developed at the ecumenical Council of Nicaea (325), and that of Constantinople (381), to distinguish Catholics from the Arian heretics who denied the consubstantiality of the Son with the Father. Later, in stages, it was adopted into the Mass, Rome being the last jurisdiction to do this in the 11th century.
Credo I of the six melodies or cantillations in the chant books dates from that 11th century and is considered the “authentic tone.” Credo III, presented here, is more familiar to us and harks back to the 17th century. It is the most widely known melody and was heard by this writer as a new priest in 1956 in St. Peter’s at the Vatican sung by memory by a huge crowd. It was a glorious sound.
Below, the Credo in Latin with music. At the bottom of the page, you can sing the Credo III.